liu_xing_hui
liu_xing_hui

5种数据库sql语句大全

数据库sql语句大全

一、连接列值
db2/oracle/postgresql
select name(字段)||' Works AS a '（文字）||job as msg from emp where deptno=10;

mysql
select concat(name,' works as a',job) as msg from emp where deptno=10;

sql server
select name+' works as a '+job as msg from emp where deptno=10;

二、使用条件逻辑
select name,salary,
     case when salary<=2000 then 'low'
     case when salary>=4000 then 'over'
       else 'ok'
     end as status
from emp

三、限制返回的行数
db2
select * from emp fetch first 5 rows only

mysql/postgresql
select * from emp limit 5

oracle
select * from emp rownum<=5

sql server
select top 5 * from emp

四、随机返回记录
db2
select name,job from emp order by rahnd() fetch first 5 rows only

mysql
select name,job from emp order by rand() limit 5

postgresql
select * from emp order by random() limit 5

oracle
select * from (select name,job from emp order by dbms_random.value()) where rownum<=5

sql server
select top 5 name,job from emp order by newid()

五、将空值转换成实际值
select coalesce(comm,0) from emp
不为空则返回comm值，空则返回0，comm类型与0类型必须一致

六、按子串排序(取消后面2位)
db2/mysql/oracle/postgresql
select name,job from emp order by substr(job,length(job)-2)

sql server
select name,job from emp order by substring(job,len(job)-2,2)

七、对字母数字混合的数据排序
oracle/postgresql

select data from emp v order by replace (data,replace(translate(data,'0123456789','##########'),'#',''),'')


select data from emp order by replace(translate(data,'0123456789','##########'),'#','')

db2

select * from (select ename||' '||cast(deptno as char(2)) as data from emp ) v order by replace (data,replace(translate(data,'##########','0123456789'),'#',''),'')


select * from (select name||' '||cast(deptno as char(2)) as data from emp v order by replace(translate(data,'##########','0123456789'),'#','')

mysql/sqlserver
当前不支持translate函数，无解决方案

八、处理排序空值
db2/mysql/postgresql/sqlserver
select name,sal,comm from (select name,sal,comm case when comm is null then 0 else 1 end as is_null from emp) x order by is_null desc,comm

oracle
select name,sal,comm from emp order by comm nulls last//all nulls last
select name,sal,comm from emp order by comm nulls first//all nulls first

九、根据数据项的键排序
select name,sal,job,comm from emp order by case when job='salesman' then comm else sal end

十、记录集的叠加
//使用union子句相当于对使用union all子句的结果使用distinct
select ename as ename_and_dname,deptno from emp where deptno=10 union all select '----------',null from t1 union all select dname,deptno from dept

十一、从一个表红查找另一个表没有的值
db2/postgresql
select deptno from dept except select deptno from emp

oracle
select deptno from dept minus select deptno from emp

mysql/sqlserver
select deptno from dept where deptno not in (select deptno from emp)

十二、在一个表中查找与其他表不匹配的记录
db2/mysql/postgresql/sqlserver
select d.* from dept d left outer join emp e on(d.deptno=e.deptno) where e.deptno is null

oracle
select d.* from dept d,emp e where d.deptno=e.deptno (+) and e.deptno is null

十三、向查询中增加联接而不影响其他联接
db2/mysql/postgresql/sqlserver
select e.ename,d.loc,eb.received from emp e join dept d on (e.deptno=d.deptno) left join emp_bonus eb on (e.empno=eb.empno) order by 2

oracle
select e.ename,d.loc,eb.received from emp e,dept d,emp_bonus eb where e.deptno=d.deptno and e.empno=eb.empno (+) order by 2
select e.ename,d.loc,(select eb.received from emp_bonus eb where eb.empno=e.empno) as received from emp e,dept d where e.deptno=d.deptno order by 2

十四、检测两个表中是否有相同的数据
解决原理：
1、首先，查找处表emp中存在而视图v中没有的行
2、然后合并（union all）在视图v中存在，而在表emp中没有的行

十五、识别和消除笛卡尔积
在from子句对表进行联接来返回正确的结果集：
select e.ename,d.loc from emp e,dept d where e.deptno=10 and d.deptno =e.deptno

十六、聚集与联接

mysql/postgresql
select deptno,sum(distinct sal) as total_sal,sum(bonus) as total_bonus from (select e.empno,e.ename,e.sal,e.deptno,e.sal*case when eb.type=1 then .1 when eb.type=2 then .2 else .3 end as bonus from emp e,emp_bonus eb where e.empno=eb.empno and e.deptno=1) x group by deptno

db2/oracle/sqlserver
select distinct deptno,total_sal,total_bonus from (select e.empno,e.ename,sum(distinct e.sal) over (partition by e.deptno) as total_sal,e.deptno,sum(e.sal*case when eb.type=1 then .1 when eb.type=2 then .2 else .3 end) over (partition by deptno) as total_bonus from emp e,emp_bonus eb where e.empno=eb.empno and e.deptno=10) x

十七、聚集与外联接

db2/mysql/postgresql/sqlserver
select deptno,sum(distinct sal) as total_sal,sum(bonus) as total_bonus from (select e.empno,e.ename,e.sal,e.deptno,e.sal*case when eb.type is null then 0 when eb.type=1 then .1 when eb.type=2 then .2 else .3 end as bonus from emp e left outer join emp_bonus eb on(e.empno=eb.empno) where e.deptno=10) group by deptno

select distinct deptno,total_sal,total_bonus from (select e.empno,e.ename,sum(distinct e.sal) over (partition by e.deptno) as total_sal,e.deptno,sum(e.sal*case when eb.type is null then 0 when eb.type=1 then .1 when eb.type =2 then .2 else .3 end) over (partition by deptno) as total_bonus from emp e left outer join emp_bonus eb on (e.empno=eb.empno) where e.deptno=10) x

oracle
select deptno,sum(distinct sal) as total_sal,sum(bonus) as total_bonus from (select e.empno,e.ename,e.sal,e.deptno,e.sal*case when eb.type is null then 0 when eb.type=1 then .1 when eb.type=2 then .2 else .3 end as bonus from emp e,emp_bonus eb where e.empno=eb.empno (+) and e.deptno=10) group by deptno

十八、从多个表中返回丢失的数据
db2/mysql/postgresql/sqlserver
select d.deptno,d.dname,e.ename from dept d full outer join emp e on (d.deptno=e.deptno)

select d.deptno,d.dname,e.ename from dept d right outer join emp e on(d.deptno=e.deptno) union select d.deptno,d.dname,e.ename from dept d left outer join emp e on (d.deptno=e.deptno)

oracle
select d.deptno,d.dname,e.ename from dept d,emp e where d.deptno=e.deptno (+) union select d.deptno,d.dname,e.ename from dept d,emp e where d.deptno(+)=e.deptno

十九、在运算和比较时使用null值
select ename,comm from emp where coalesce(comm,0)<(select comm from emp where ename='WARD')

二十、从一个表向另外的表中复制行
insert into dept_east (deptno,dname,loc) select deptno,dname,loc from dept where loc in('NEW YORK','BOSTON')

二十一、复制表定义
db2
create table dept_2 like dept

oracle/mysql/postgresql
create table dept_2 as select * from dept where 1=0

sqlserver
select * into dept_2 from dept where 1=0

二十二、一次向多个表中插入记录
oracle
insert all when loc in('NEW YORK','BOSTON') then into dept_east (deptno,dname,loc) values(deptno,dname,loc)
when loc='CHICAGO' then into dept_mid (deptno,dname,loc) values(deptno,dname,loc)
else into dept_west (deptno,dname,loc) values(deptno,dname,loc)
select deptno,dname,loc from dept

db2
insert into (select * from dept_west union all select * from dept_east union all select * from dept_mid) select * from dept

mysql/postgresql/sqlserver
不支持多表插入操作

二十三、阻止对某几列插入
在表中创建一个视图，该视图将只显示允许用户进行操作的列，强制所有的插入操作都通过该视图进行
create view new_emps as select empno,ename,job from emp

 

二十四、用其他表中的值更新
db2/mysql
update emp e set(e.sal,e.comm)=(select ns.sal,ns.sal/2 from new_sal ns where ns.deptno=e.deptno) where exists(select nul from new_sa ns where ns.deptno=e.deptno)

oracle
update(select e.sal as emp_sal,e.comm as emp_comm,ns.sal as ns_sal,ns.sal/2 as ns_comm frm emp e,new_sal ns where e.deptno=ns.deptno) set emp_sal=ns_sal,emp_comm=ns_comm

postgresql
update emp set sal=ns.sal,comm=ns.sal/2 from new_sal ns where ns.deptno=emp.deptno

sqlserver
update e set e.sal=ns.sal,e.comm=ns.sal/2 from emp e,new_sal ns where ns.deptno=emp.deptno

二十五、合并记录
oracle
merge into emp_commission ec using(select * from emp) emp on(ec.empno=emp.empno) when matched then update set ec.comm=1000 delete where (sal<2000) when not matched then insert (ec.empno,ec.ename,ec.deptno,ec.comm) values (emp.empno,emp.ename,emp.deptno,emp.comm)

二十六、删除违反参照完整性的记录
delete from emp where not exists(select * from dept where dept.deptno=emp.deptno)

delete from emp where deptno not in(select deptno from dept)

二十七、删除重复记录
delete from dupes where id not in (select min(id) from dupes group by name(需要判断重复的字段))

二十八、删除从其他表引用的记录
delete from emp where deptno in (select deptno from dept_accidents group by deptno having count(*)>=3)

（以下模式名schema为smeagol）
二十九、列出模式中的表
db2
select tabname from syscat.table where tabschema='smeagol'

oracle
select table_name from all_tables where owner='smeagol'

postgresql/mysql/sqlserver
select tablename from information_schema.tables where table_schema='smeagol'

三十、列出表的列
db2
select colname,typename,colno from syscat.columns where tablename='emp' and tabschema='smeagol'

oracle
select column_name,data_type,column_id from all_tab_columns where owner='smeagol' and table_name='emp'

postgresql/mysql/sqlserver
select column_name,data_type,ordinal_position from information_schema='smeagol' and table_name='emp'

三十一、列出表的索引列
db2
select a.tabname,b.indname,b.colname,b.colseq from syscat.indexes a,syscat.indexcoluse b where a.tabname='emp' and a.tabschema='smeagol' and a.indschema=b.indschema and a.indname=b.indname

oracle
select table_name,index_name,column_name,column_position from sys.all_ind_columns where table_name='emp' and table_owner='smeagol'

postgresql
select a.tablename,a.indexname,b.column_name from pg_catalog.pg_indexes a,information_schema.columns b where a.schemaname='smeagol' and a.tablename=b.table_name

mysql
show index from emp

sqlserver
select a.name table_name,b.name index_name,d.name column_name,c.index_column_id from sys.tables a,sys.indexes b,sys.index_columns c,sys.columns d where a.object_id=b.object_id and b.object_id=c.object_id and b.index_id=c.index_id and c.object_id=d.object_id and c.column_id=d.column_id and a.name='emp'

三十二、列出表约束
db2
select a.tabname,a.constname,b.colname,a.type from syscat.tabconst a,syscat.columns b where a.tabname='emp' and a.tabschema='smeagol' and a.tabname=b.tabname and a.tabschema=b.tabschema

oracle
select a.table_name,a.constraint_name,b.column_name,a.constraint_type from all_constraints a,all_cons_columns b where a.table_name='emp' and a.owner='smeagol' and a.table_name=b.table_name and a.owner=b.owner and a.constraint_name=b.constraint_name

postgresql/mysql/sqlserver
select a.table_name,a.constraint_name,b.column_name,a.constraint_type from information_schema.table_constraints a,information_schema.key_column_usage b where a.table_name='emp' and a.table_schema='smeagol' and a.table_name=b.table_name and a.table_schema=b.table_schema and a.constraint_name=b.constraint_name

三十三、列出没有相应索引的外键
db2
select fkeys.tabname,fkeys.constname,fkeys.colname,ind_cols.indname from (select a.tabschema,a.tabname,a.constname,b.colname from syscat.tabconst a,syscat.keycoluse b where a.tabname='emp' and a.tabschema='smeagol' and a.type='f' and a.tabname=b.tabname and a.tabschema=b.tabschema) fkeys left join (select a.tabschema,a.tabname,a.indname,b.colname from syscat.indexes a,syscat.indexcoluse b where a.indschema=b.indschema and a.indname=b.indname) ind_cols on(fkeys.tabschema=ind_cols.tabschema and fkeys.tabname=ind_cols.tabname and fkeys.colname=ind_cols.colname)where ind_cols.indname is null

oracle
select a.table_name,a.constraint_name,a.column_name,c.index_name from all_cons_columns a,all_constraints b,all_ind_columns c where a.table_name='emp' and a.owner='smeagol' and b.constraint_type='r' and a.owner=b.owner and a.table_name=b.table_name and a.constraint_name=b.constraint_name and a.owner=c.table_owner(+) and a.table_name=c.table_name(+) and a.column_name=c.column_name(+) and c.index_name is null

postgresql
select fkeys.table_name,fkeys.constraint_name,fkeys.column_name,ind_cols.index_name from (select a.constraint_schema,a.table_name,a.constraint_name,a.column_name from information_schema.key_column_usage a,information_schema.referential_constraints b where a.table_name='emp' and a.constraint_schema='smeagol' and a.constraint_name=b.constraint_name and a.constraint_schema=b.constraint_schema) fkeys left join (select a.schemaname,a.tablename,a.indexname,b.column_name from pg_catalog.pg_indexes a,information_schema.columns b where a.schemaname=b.table_schema and a.tablename=b.table_name) ind_cols on(fkeys.constraint_schema=ind_cols.schemaname and fkeys.table_name=ind_cols.tablename and fkeys.column_name=ind_cols.column_name)where ind_cols.indexname is null

mysql
使用show index来检索索引信息，查询information——schema.key_column_usage列出指定表的外键

sqlserver
select fkeys.table_name,fkeys.constraint_name,fkeys.column_name,ind_cols.index_name from (select a.object_id,d.column_id,a.name table_name,b.name constraint_name,d.name column_name from sys.tables a join sys.foreign_keys b on (a.name='emp' and a.object_id=b.parent_object_id) join sys.foreign_key_columns c on(b.object_id=c.constraint_object_id) join sys.columns d on (c.constraint_column_id=d.column_id and a.object_id=d.object_id) fkeys left join (select a.name index_name,b.object_id,b.column_id from sys.indexes a,sys.index_columns b where a.index_id=b.index_id) ind_cols on (fkeys.object_id=ind_cols.object_id and fkeys.column_i=ind_cols.column_id) where ind_cols.index_name is null

三十四、使用sql来生成sql
oracle
select 'select count(*) from '||table_name||';' cnts from user_tables;

三十五、在oracle中描述数据字典视图
select table_name,comments from dictionary order by table_name

select column_name,comments from dict_columns where table_name='all_tab_columns'

三十六、遍历字符串
select substr(e.ename,iter.post,1) as c from (select ename from emp where ename='king') e,(select id as pos from t10) iter where iter.pos<=length(e.ename)

三十七、计算字符在字符串中出现的次数
select (length('10,clark,manager')-length(replace('10,clark,manager',',','')))/length(',') as cnt from t1

三十八、从字符串中删除不需要的字符
db2
select ename,replace(translate(ename,'aaaaa','AEIOU'),'a','') stripped1,sal,replace(cast(sal as char(4)),'0','') stripped2 from emp

mysql/sqlserver
select ename,replace(replace(replace(replace(replace(ename,'A',''),'E',''),'I',''),'O',''),'U','') as stripped1,sal,replace(sal,0,'') stripped2 from emp

oracle/postgresql
select ename,replace(translate(ename,'AEIOU','aaaa'),'a') as stripped1,sal,replace(sal,0,'') as stripped2 from emp

三十九、将字符和数字数据分离
db2
select replace(translate(data,'0000000000','0123456789'),'0','') ename,cast(replace(translate(lower(data),repeat('z',26),'abcdefghijklmnopqrstuvwxyz'),'z','') as integer) sal from (select ename||cast(sal as char(4)) data from emp) x

oracle
select replace(translate(data,'0123456789','0000000000'),'0') ename,to_number(replace(translate(lower(data),'abcdefghijklmnopqrstuvwxyz',rpad('z',26,'z')),'z')) sal from (select ename||sal data from emp)

postgresql
select replace(translate(data,'0123456789','0000000000'),'0','') as ename,cast(replace(translate(lower(data),'abcdefghijklmnopqrstuvwxyz',rpad('z',26,'z')),'z','') as integer) as sal from (select ename||sal as data from emp) x

四十、判断字符串是不是字母数字型的
db2
select data from view where translate(lower(data),repeat('a',36),'0123456789abcdefghijklmnopqrstuvwxyz')=repeat('a',length(data))

mysql
create view V as select ename as data from emp where deptno=10 union all select concat(ename,',$',sal,'.00') as data from emp where deptno=20 union all select concat(ename,deptno) as data from emp where deptno=30
select data from V where data regexp '[^0-9a-zA-Z]'=0

oracle/postgresql
select data from V where translate(lower(data),'0123456789abcdefghijklmnopqrstuvwxyz',rpad('a',36,'a'))=rpad('a',length(data),'a')

sqlserver
select data from (select v.data,iter.pos,substring(v.data,iter.pos,1) c,ascii(substring(v.data,iter.pos,1)) val from v,(select id as pos from t100) iter where iter.pos<=len(v.data)) x group by data having min(val) between 48 and 122

四十一、提取姓名的大写首字母缩写
db2
select replace(replace(translate(replace('Stewie Griffin','.',''),repeat('#',26),'abcdefghijklmnopqrstuvwxyz'),'#',''),' ','.')||'.' from dual

mysql
select case when cnt=2 then trim(trailing '.' from concat_ws('.',substr(substring_index(name,' ',1),1,1),substr(name,length(substring_index(name,' ',1))+2,1),substr(substring_index(name,' ',-1),1,1),'.')) else trim(trailing '.' from concat_ws('.',substr(substring_index(name,' ',1),1,1),substr(substring_index(name,' ',-1),1,1))) end as initials from (select name,length(name)-length(replace(name,' ','')) as cnt from (select replace('Stewie Griffin','.','') as name from dual ) y ) x

oracle/postgresql
select replace(replace(translate(replace('Stewie Griffin','.',''),'abcdefghijklmnopqrstuvwxyz',rpad('#',26,'#')),'#',''),' ','.')||'.' from dual

四十二、按字符串中的部分内容排序
db2/oracle/mysql/postgresql
select ename from emp order by substr(ename,length(ename)-1,2)

sqlserver
select ename from emp order by substring(ename,len(ename)-1,2)

四十三、按字符串中的数值排序
db2
select data from V order by cast(replace(translate(data,repeat('#',length(data)),replace(translate(data,'##########','0123456789'),'#','')),'#','') as integer)

oracle
select data from V order by to_number(replace(translate(data,replace(translate(data,'0123456789','##########'),'#'),rpad('#',20,'#')),'#'))

postgresql
select data from V order by cast(replace(translate(data,replace(translate(data,'0123456789','##########'),'#',''),rpad('#',20,'#')),'#','') as integer)

四十四、根据表中的行创建一个分割列表
db2
with x (deptno,cnt,list,empno,len) as (select deptno,count(*) over (partition by deptno), cast(ename as varchar(100)),empno,1 from emp union all select x.deptno,x.cnt,x.list||','||e.name,e.empno,x.len+1 from emp e,x where e.deptno=x.deptno and e.empno>x.empno) select deptno,list from x where len=cnt

mysql
select deptno,group_concat(ename order by empno separator,',') as emps from emp group by deptno

oracle
select deptno,ltrim(sys_connect_by_path(ename,','),',') emps from (select deptno,ename,row_number() over (partition by deptno order by empno) rn,count(*) over (partition by deptno) cnt from emp) where level=cnt start with rn=1 connect by prior deptno=deptno and prior rn=rn-1

postgresql
select deptno,rtrim(max(case when pos=1 then emps else '' end)||max(case when pos=2 then emps else '' end)||max(case when pos=3 then emps else '' end)||max(case when pos=4 then emps else '' end)||max(case when pos=5 then emps else '' end)||max(case when pos=6 then emps else '' end),',') as emps from (select a.deptno,a.ename||',' as emps,d.cnt,(select count(*) from emp b where a.deptno=b.deptno and b.empno<=empno ) as pos from emp a,(select deptno,count(ename) as cnt from emp group by deptno) d where d.deptno=a.deptno) x group by deptno order by 1

sqlserver
with x (deptno,cnt,list,empno,len) as (select deptno,count(*) over (partition by deptno), cast(ename as varchar(100)),empno,1 from emp union all select x.deptno,x.cnt,cast(x.list+','+e.name as varchar(100)),e.empno,x.len+1 from emp e,x where e.deptno=x.deptno and e.empno>x.empno) select deptno,list from x where len=cnt order by 1

四十五、将分隔数据转换为多值IN列表
db2
select empno,ename,sal,deptno from emp where empno in (select cast(substr(c,2,locate(',',c,2)-2) as integer) empno from (select substr(csv.emps,cast(iter.pos as integer)) as c from (select ','||'7654,7698,7782,7788'||',' emps from t1 ) csv,(select id as pos from t100) iter where iter.pos<=length(csv.emps)) x where length(c)>1 and substr(c,1,1)=',' ) y

mysql
select empno,ename,sal,deptno from emp where empno in (select substring_index(substring_index(list.vals,',',iter.pos),',',-1) empno from (select id pos from t10) as iter,(select '7654,7698,7782,7788' as vals from t1) list where iter.pos<=(length(list.vals)-length(replace(list.vals,',','')))+1) x

oracle
select empno,ename,sal,deptno from emp where empno in (select to_number(rtrim(substr(emps,instr(emps,',',1,iter.pos)+1,instr(emps,',',1,iter.pos+1)-instr(emps,',',1,iter.pos)),',')) emps from (select ','||'7654,7698,7782,7788'||',' emps from t1) csv,(select rownum pos from emp) iter where iter.pos<=((length(csv.emps)-length(replace(csv.emps,',')))/length(','))-1

postgresql
select empno,ename,sal,deptno from emp where empno in (select cast (empno as integer) as empno from (select split_part(list.vals,',',iter.pos) as empno from (select id as pos from t10) iter,(select ','||'7654,7698,7782,7788'||',' as vals from t1) list where iter.pos<=length(list.vals)-length(replace(ist.vals,',',''))) z where length(empno)>0) x

sqlserver
select empno,ename,sal,deptno from emp where empno in (select substring(c,2,charindex(',',c,2)-2) as empno from (select substring(csv.emps,iter.pos,len(csv.emps)) as c from (select ','+'7654,7698,7782,7788'+',' as emps from t1) csv,(select id as pos from t100) iter where iter.pos<=len(csv.emps)) x where len(c)>1 and substring(c,1,1)=',') y

四十六、按字母顺序排列字符串
db2
select ename,max(case when pos=1 then c else '' end)||max(case when pos=2 then c else '' end)||max(case when pos=3 then c else '' end)||max(case when pos=4 then c else '' end)||max(case when pos=5 then c else '' end)||max(case when pos=6 then c else '' end) from (select e.ename,cast(substr(e.ename,iter.pos,1) as varchar(100)) c,cast(row_number() over (partition by e.ename order by substr(e.ename,iter.pos,1)) as integer) pos from emp e,(select cast(row_number() over() as integer) pos from emp) iter where iter.pos<=length(e.ename)) x group by ename

mysql
select ename,group_concat(c order by c separator '') from ( select ename,substr(a.ename,iter.pos,1) c from emp a,(select id pos from t10) iter where iter.pos<=length(a.ename)) x group by ename

oracle
select old_name,new_name from (select old_name,replace(sys_connect-by_path(c,' '),' ') new_name from (select e.ename old_name,row_number() over(partition by e.ename order by substr(e.ename,iter.pos,1)) rn,substr(e.ename,iter.pos,1) c from emp e,(select rownum pos from emp) iter where iter.pos<=length(e.ename) order by 1) x start with rn=1 connect by prior rn=rn-1 and prior old_name=old_name) where length(old_name)=length(new_name)

postgresql
必须先遍历每个字符串，先要知道姓名的最大长度

sqlserver
select ename,max(case when pos=1 then c else '' end)+max(case when pos=2 then c else '' end)+max(case when pos=3 then c else '' end)+max(case when pos=4 then c else '' end)+max(case when pos=5 then c else '' end)+max(case when pos=6 then c else '' end) from (select e.ename,substring(e.ename,iter.pos,1) as c,row_number() over (partition by e.ename order by substring(e.ename,iter.pos,1)) as pos from emp e,(select row_number() over(order by ename) as pos from emp) iter where iter.pos<=len(e.ename)) x group by ename

二十四、用其他表中的值更新
db2/mysql
update emp e set(e.sal,e.comm)=(select ns.sal,ns.sal/2 from new_sal ns where ns.deptno=e.deptno) where exists(select nul from new_sa ns where ns.deptno=e.deptno)

oracle
update(select e.sal as emp_sal,e.comm as emp_comm,ns.sal as ns_sal,ns.sal/2 as ns_comm frm emp e,new_sal ns where e.deptno=ns.deptno) set emp_sal=ns_sal,emp_comm=ns_comm

postgresql
update emp set sal=ns.sal,comm=ns.sal/2 from new_sal ns where ns.deptno=emp.deptno

sqlserver
update e set e.sal=ns.sal,e.comm=ns.sal/2 from emp e,new_sal ns where ns.deptno=emp.deptno

二十五、合并记录
oracle
merge into emp_commission ec using(select * from emp) emp on(ec.empno=emp.empno) when matched then update set ec.comm=1000 delete where (sal<2000) when not matched then insert (ec.empno,ec.ename,ec.deptno,ec.comm) values (emp.empno,emp.ename,emp.deptno,emp.comm)

二十六、删除违反参照完整性的记录
delete from emp where not exists(select * from dept where dept.deptno=emp.deptno)

delete from emp where deptno not in(select deptno from dept)

二十七、删除重复记录
delete from dupes where id not in (select min(id) from dupes group by name(需要判断重复的字段))

二十八、删除从其他表引用的记录
delete from emp where deptno in (select deptno from dept_accidents group by deptno having count(*)>=3)

（以下模式名schema为smeagol）
二十九、列出模式中的表
db2
select tabname from syscat.table where tabschema='smeagol'

oracle
select table_name from all_tables where owner='smeagol'

postgresql/mysql/sqlserver
select tablename from information_schema.tables where table_schema='smeagol'

三十、列出表的列
db2
select colname,typename,colno from syscat.columns where tablename='emp' and tabschema='smeagol'

oracle
select column_name,data_type,column_id from all_tab_columns where owner='smeagol' and table_name='emp'

postgresql/mysql/sqlserver
select column_name,data_type,ordinal_position from information_schema='smeagol' and table_name='emp'

三十一、列出表的索引列
db2
select a.tabname,b.indname,b.colname,b.colseq from syscat.indexes a,syscat.indexcoluse b where a.tabname='emp' and a.tabschema='smeagol' and a.indschema=b.indschema and a.indname=b.indname

oracle
select table_name,index_name,column_name,column_position from sys.all_ind_columns where table_name='emp' and table_owner='smeagol'

postgresql
select a.tablename,a.indexname,b.column_name from pg_catalog.pg_indexes a,information_schema.columns b where a.schemaname='smeagol' and a.tablename=b.table_name

mysql
show index from emp

sqlserver
select a.name table_name,b.name index_name,d.name column_name,c.index_column_id from sys.tables a,sys.indexes b,sys.index_columns c,sys.columns d where a.object_id=b.object_id and b.object_id=c.object_id and b.index_id=c.index_id and c.object_id=d.object_id and c.column_id=d.column_id and a.name='emp'

三十二、列出表约束
db2
select a.tabname,a.constname,b.colname,a.type from syscat.tabconst a,syscat.columns b where a.tabname='emp' and a.tabschema='smeagol' and a.tabname=b.tabname and a.tabschema=b.tabschema

oracle
select a.table_name,a.constraint_name,b.column_name,a.constraint_type from all_constraints a,all_cons_columns b where a.table_name='emp' and a.owner='smeagol' and a.table_name=b.table_name and a.owner=b.owner and a.constraint_name=b.constraint_name

postgresql/mysql/sqlserver
select a.table_name,a.constraint_name,b.column_name,a.constraint_type from information_schema.table_constraints a,information_schema.key_column_usage b where a.table_name='emp' and a.table_schema='smeagol' and a.table_name=b.table_name and a.table_schema=b.table_schema and a.constraint_name=b.constraint_name

三十三、列出没有相应索引的外键
db2
select fkeys.tabname,fkeys.constname,fkeys.colname,ind_cols.indname from (select a.tabschema,a.tabname,a.constname,b.colname from syscat.tabconst a,syscat.keycoluse b where a.tabname='emp' and a.tabschema='smeagol' and a.type='f' and a.tabname=b.tabname and a.tabschema=b.tabschema) fkeys left join (select a.tabschema,a.tabname,a.indname,b.colname from syscat.indexes a,syscat.indexcoluse b where a.indschema=b.indschema and a.indname=b.indname) ind_cols on(fkeys.tabschema=ind_cols.tabschema and fkeys.tabname=ind_cols.tabname and fkeys.colname=ind_cols.colname)where ind_cols.indname is null

oracle
select a.table_name,a.constraint_name,a.column_name,c.index_name from all_cons_columns a,all_constraints b,all_ind_columns c where a.table_name='emp' and a.owner='smeagol' and b.constraint_type='r' and a.owner=b.owner and a.table_name=b.table_name and a.constraint_name=b.constraint_name and a.owner=c.table_owner(+) and a.table_name=c.table_name(+) and a.column_name=c.column_name(+) and c.index_name is null

postgresql
select fkeys.table_name,fkeys.constraint_name,fkeys.column_name,ind_cols.index_name from (select a.constraint_schema,a.table_name,a.constraint_name,a.column_name from information_schema.key_column_usage a,information_schema.referential_constraints b where a.table_name='emp' and a.constraint_schema='smeagol' and a.constraint_name=b.constraint_name and a.constraint_schema=b.constraint_schema) fkeys left join (select a.schemaname,a.tablename,a.indexname,b.column_name from pg_catalog.pg_indexes a,information_schema.columns b where a.schemaname=b.table_schema and a.tablename=b.table_name) ind_cols on(fkeys.constraint_schema=ind_cols.schemaname and fkeys.table_name=ind_cols.tablename and fkeys.column_name=ind_cols.column_name)where ind_cols.indexname is null

mysql
使用show index来检索索引信息，查询information——schema.key_column_usage列出指定表的外键

sqlserver
select fkeys.table_name,fkeys.constraint_name,fkeys.column_name,ind_cols.index_name from (select a.object_id,d.column_id,a.name table_name,b.name constraint_name,d.name column_name from sys.tables a join sys.foreign_keys b on (a.name='emp' and a.object_id=b.parent_object_id) join sys.foreign_key_columns c on(b.object_id=c.constraint_object_id) join sys.columns d on (c.constraint_column_id=d.column_id and a.object_id=d.object_id) fkeys left join (select a.name index_name,b.object_id,b.column_id from sys.indexes a,sys.index_columns b where a.index_id=b.index_id) ind_cols on (fkeys.object_id=ind_cols.object_id and fkeys.column_i=ind_cols.column_id) where ind_cols.index_name is null

三十四、使用sql来生成sql
oracle
select 'select count(*) from '||table_name||';' cnts from user_tables;

三十五、在oracle中描述数据字典视图
select table_name,comments from dictionary order by table_name

select column_name,comments from dict_columns where table_name='all_tab_columns'

三十六、遍历字符串
select substr(e.ename,iter.post,1) as c from (select ename from emp where ename='king') e,(select id as pos from t10) iter where iter.pos<=length(e.ename)

三十七、计算字符在字符串中出现的次数
select (length('10,clark,manager')-length(replace('10,clark,manager',',','')))/length(',') as cnt from t1

三十八、从字符串中删除不需要的字符
db2
select ename,replace(translate(ename,'aaaaa','AEIOU'),'a','') stripped1,sal,replace(cast(sal as char(4)),'0','') stripped2 from emp

mysql/sqlserver
select ename,replace(replace(replace(replace(replace(ename,'A',''),'E',''),'I',''),'O',''),'U','') as stripped1,sal,replace(sal,0,'') stripped2 from emp

oracle/postgresql
select ename,replace(translate(ename,'AEIOU','aaaa'),'a') as stripped1,sal,replace(sal,0,'') as stripped2 from emp

三十九、将字符和数字数据分离
db2
select replace(translate(data,'0000000000','0123456789'),'0','') ename,cast(replace(translate(lower(data),repeat('z',26),'abcdefghijklmnopqrstuvwxyz'),'z','') as integer) sal from (select ename||cast(sal as char(4)) data from emp) x

oracle
select replace(translate(data,'0123456789','0000000000'),'0') ename,to_number(replace(translate(lower(data),'abcdefghijklmnopqrstuvwxyz',rpad('z',26,'z')),'z')) sal from (select ename||sal data from emp)

postgresql
select replace(translate(data,'0123456789','0000000000'),'0','') as ename,cast(replace(translate(lower(data),'abcdefghijklmnopqrstuvwxyz',rpad('z',26,'z')),'z','') as integer) as sal from (select ename||sal as data from emp) x

四十、判断字符串是不是字母数字型的
db2
select data from view where translate(lower(data),repeat('a',36),'0123456789abcdefghijklmnopqrstuvwxyz')=repeat('a',length(data))

mysql
create view V as select ename as data from emp where deptno=10 union all select concat(ename,',$',sal,'.00') as data from emp where deptno=20 union all select concat(ename,deptno) as data from emp where deptno=30
select data from V where data regexp '[^0-9a-zA-Z]'=0

oracle/postgresql
select data from V where translate(lower(data),'0123456789abcdefghijklmnopqrstuvwxyz',rpad('a',36,'a'))=rpad('a',length(data),'a')

sqlserver
select data from (select v.data,iter.pos,substring(v.data,iter.pos,1) c,ascii(substring(v.data,iter.pos,1)) val from v,(select id as pos from t100) iter where iter.pos<=len(v.data)) x group by data having min(val) between 48 and 122

四十一、提取姓名的大写首字母缩写
db2
select replace(replace(translate(replace('Stewie Griffin','.',''),repeat('#',26),'abcdefghijklmnopqrstuvwxyz'),'#',''),' ','.')||'.' from dual

mysql
select case when cnt=2 then trim(trailing '.' from concat_ws('.',substr(substring_index(name,' ',1),1,1),substr(name,length(substring_index(name,' ',1))+2,1),substr(substring_index(name,' ',-1),1,1),'.')) else trim(trailing '.' from concat_ws('.',substr(substring_index(name,' ',1),1,1),substr(substring_index(name,' ',-1),1,1))) end as initials from (select name,length(name)-length(replace(name,' ','')) as cnt from (select replace('Stewie Griffin','.','') as name from dual ) y ) x

oracle/postgresql
select replace(replace(translate(replace('Stewie Griffin','.',''),'abcdefghijklmnopqrstuvwxyz',rpad('#',26,'#')),'#',''),' ','.')||'.' from dual

四十二、按字符串中的部分内容排序
db2/oracle/mysql/postgresql
select ename from emp order by substr(ename,length(ename)-1,2)

sqlserver
select ename from emp order by substring(ename,len(ename)-1,2)

四十三、按字符串中的数值排序
db2
select data from V order by cast(replace(translate(data,repeat('#',length(data)),replace(translate(data,'##########','0123456789'),'#','')),'#','') as integer)

oracle
select data from V order by to_number(replace(translate(data,replace(translate(data,'0123456789','##########'),'#'),rpad('#',20,'#')),'#'))

postgresql
select data from V order by cast(replace(translate(data,replace(translate(data,'0123456789','##########'),'#',''),rpad('#',20,'#')),'#','') as integer)

四十四、根据表中的行创建一个分割列表
db2
with x (deptno,cnt,list,empno,len) as (select deptno,count(*) over (partition by deptno), cast(ename as varchar(100)),empno,1 from emp union all select x.deptno,x.cnt,x.list||','||e.name,e.empno,x.len+1 from emp e,x where e.deptno=x.deptno and e.empno>x.empno) select deptno,list from x where len=cnt

mysql
select deptno,group_concat(ename order by empno separator,',') as emps from emp group by deptno

oracle
select deptno,ltrim(sys_connect_by_path(ename,','),',') emps from (select deptno,ename,row_number() over (partition by deptno order by empno) rn,count(*) over (partition by deptno) cnt from emp) where level=cnt start with rn=1 connect by prior deptno=deptno and prior rn=rn-1

postgresql
select deptno,rtrim(max(case when pos=1 then emps else '' end)||max(case when pos=2 then emps else '' end)||max(case when pos=3 then emps else '' end)||max(case when pos=4 then emps else '' end)||max(case when pos=5 then emps else '' end)||max(case when pos=6 then emps else '' end),',') as emps from (select a.deptno,a.ename||',' as emps,d.cnt,(select count(*) from emp b where a.deptno=b.deptno and b.empno<=empno ) as pos from emp a,(select deptno,count(ename) as cnt from emp group by deptno) d where d.deptno=a.deptno) x group by deptno order by 1

sqlserver
with x (deptno,cnt,list,empno,len) as (select deptno,count(*) over (partition by deptno), cast(ename as varchar(100)),empno,1 from emp union all select x.deptno,x.cnt,cast(x.list+','+e.name as varchar(100)),e.empno,x.len+1 from emp e,x where e.deptno=x.deptno and e.empno>x.empno) select deptno,list from x where len=cnt order by 1

四十五、将分隔数据转换为多值IN列表
db2
select empno,ename,sal,deptno from emp where empno in (select cast(substr(c,2,locate(',',c,2)-2) as integer) empno from (select substr(csv.emps,cast(iter.pos as integer)) as c from (select ','||'7654,7698,7782,7788'||',' emps from t1 ) csv,(select id as pos from t100) iter where iter.pos<=length(csv.emps)) x where length(c)>1 and substr(c,1,1)=',' ) y

mysql
select empno,ename,sal,deptno from emp where empno in (select substring_index(substring_index(list.vals,',',iter.pos),',',-1) empno from (select id pos from t10) as iter,(select '7654,7698,7782,7788' as vals from t1) list where iter.pos<=(length(list.vals)-length(replace(list.vals,',','')))+1) x

oracle
select empno,ename,sal,deptno from emp where empno in (select to_number(rtrim(substr(emps,instr(emps,',',1,iter.pos)+1,instr(emps,',',1,iter.pos+1)-instr(emps,',',1,iter.pos)),',')) emps from (select ','||'7654,7698,7782,7788'||',' emps from t1) csv,(select rownum pos from emp) iter where iter.pos<=((length(csv.emps)-length(replace(csv.emps,',')))/length(','))-1

postgresql
select empno,ename,sal,deptno from emp where empno in (select cast (empno as integer) as empno from (select split_part(list.vals,',',iter.pos) as empno from (select id as pos from t10) iter,(select ','||'7654,7698,7782,7788'||',' as vals from t1) list where iter.pos<=length(list.vals)-length(replace(ist.vals,',',''))) z where length(empno)>0) x

sqlserver
select empno,ename,sal,deptno from emp where empno in (select substring(c,2,charindex(',',c,2)-2) as empno from (select substring(csv.emps,iter.pos,len(csv.emps)) as c from (select ','+'7654,7698,7782,7788'+',' as emps from t1) csv,(select id as pos from t100) iter where iter.pos<=len(csv.emps)) x where len(c)>1 and substring(c,1,1)=',') y

四十六、按字母顺序排列字符串
db2
select ename,max(case when pos=1 then c else '' end)||max(case when pos=2 then c else '' end)||max(case when pos=3 then c else '' end)||max(case when pos=4 then c else '' end)||max(case when pos=5 then c else '' end)||max(case when pos=6 then c else '' end) from (select e.ename,cast(substr(e.ename,iter.pos,1) as varchar(100)) c,cast(row_number() over (partition by e.ename order by substr(e.ename,iter.pos,1)) as integer) pos from emp e,(select cast(row_number() over() as integer) pos from emp) iter where iter.pos<=length(e.ename)) x group by ename

mysql
select ename,group_concat(c order by c separator '') from ( select ename,substr(a.ename,iter.pos,1) c from emp a,(select id pos from t10) iter where iter.pos<=length(a.ename)) x group by ename

oracle
select old_name,new_name from (select old_name,replace(sys_connect-by_path(c,' '),' ') new_name from (select e.ename old_name,row_number() over(partition by e.ename order by substr(e.ename,iter.pos,1)) rn,substr(e.ename,iter.pos,1) c from emp e,(select rownum pos from emp) iter where iter.pos<=length(e.ename) order by 1) x start with rn=1 connect by prior rn=rn-1 and prior old_name=old_name) where length(old_name)=length(new_name)

postgresql
必须先遍历每个字符串，先要知道姓名的最大长度

sqlserver
select ename,max(case when pos=1 then c else '' end)+max(case when pos=2 then c else '' end)+max(case when pos=3 then c else '' end)+max(case when pos=4 then c else '' end)+max(case when pos=5 then c else '' end)+max(case when pos=6 then c else '' end) from (select e.ename,substring(e.ename,iter.pos,1) as c,row_number() over (partition by e.ename order by substring(e.ename,iter.pos,1)) as pos from emp e,(select row_number() over(order by ename) as pos from emp) iter where iter.pos<=len(e.ename)) x group by ename


 


你可能感兴趣的:(sql,数据库,schema,db2,Integer,constraints)

  • mysql禁用远程登录 igotyback mysql
    去mysql库中的user表里，将host都改成localhost之后刷新权限FLUSHPRIVILEGES;
  • Google earth studio 简介 陟彼高冈yu 旅游
    GoogleEarthStudio是一个基于Web的动画工具，专为创作使用GoogleEarth数据的动画和视频而设计。它利用了GoogleEarth强大的三维地图和卫星影像数据库，使用户能够轻松地创建逼真的地球动画、航拍视频和动态地图可视化。网址为https://www.google.com/earth/studio/。GoogleEarthStudio是一个基于Web的动画工具，专为创作使用G
  • 关于提高复杂业务逻辑代码可读性的思考 编程经验分享 开发经验java数据库开发语言
    目录前言需求场景常规写法拆分方法领域对象总结前言实际工作中大部分时间都是在写业务逻辑，一般都是三层架构，表示层（Controller）接收客户端请求，并对入参做检验，业务逻辑层（Service）负责处理业务逻辑，一般开发都是在这一层中写具体的业务逻辑。数据访问层（Dao）是直接和数据库交互的，用于查数据给业务逻辑层，或者是将业务逻辑层处理后的数据写入数据库。简单的增删改查接口不用多说，基本上写好一
  • SQL Server_查询某一数据库中的所有表的内容 qq_42772833 SQLServer数据库sqlserver
    1.查看所有表的表名要列出CrabFarmDB数据库中的所有表（名），可以使用以下SQL语句：USECrabFarmDB;--切换到目标数据库GOSELECTTABLE_NAMEFROMINFORMATION_SCHEMA.TABLESWHERETABLE_TYPE='BASETABLE';对这段SQL脚本的解释：SELECTTABLE_NAME：这个语句的作用是从查询结果中选择TABLE_NAM
  • 深入理解 MultiQueryRetriever：提升向量数据库检索效果的强大工具 nseejrukjhad 数据库python
    深入理解MultiQueryRetriever：提升向量数据库检索效果的强大工具引言在人工智能和自然语言处理领域，高效准确的信息检索一直是一个关键挑战。传统的基于距离的向量数据库检索方法虽然广泛应用，但仍存在一些局限性。本文将介绍一种创新的解决方案：MultiQueryRetriever，它通过自动生成多个查询视角来增强检索效果，提高结果的相关性和多样性。MultiQueryRetriever的工
  • MYSQL面试系列-04 king01299 面试mysql面试
    MYSQL面试系列-0417.关于redolog和binlog的刷盘机制、redolog、undolog作用、GTID是做什么的？innodb_flush_log_at_trx_commit及sync_binlog参数意义双117.1innodb_flush_log_at_trx_commit该变量定义了InnoDB在每次事务提交时，如何处理未刷入（flush）的重做日志信息（redolog）。它
  • MongoDB Oplog 窗口 喝醉酒的小白 MongoDB运维
    在MongoDB中，oplog（操作日志）是一个特殊的日志系统，用于记录对数据库的所有写操作。oplog允许副本集成员（通常是从节点）应用主节点上已经执行的操作，从而保持数据的一致性。它是MongoDB副本集实现数据复制的基础。MongoDBOplog窗口oplog窗口是指在MongoDB副本集中，从节点可以用来同步数据的时间范围。这个窗口通常由以下因素决定：Oplog大小：oplog的大小是有限
  • python os 环境变量 CV矿工 python开发语言numpy
    环境变量：环境变量是程序和操作系统之间的通信方式。有些字符不宜明文写进代码里，比如数据库密码，个人账户密码，如果写进自己本机的环境变量里，程序用的时候通过os.environ.get（）取出来就行了。os.environ是一个环境变量的字典。环境变量的相关操作importos"""设置/修改环境变量：os.environ[‘环境变量名称’]=‘环境变量值’#其中key和value均为string类
  • 【PG】常见数据库、表属性设置 江无羡 数据库
    PG的常见属性配置方法数据库复制、备份相关表的复制标识单表操作批量表操作链接数据库复制、备份相关表的复制标识单表操作通过ALTER语句单独更改一张表的复制标识。ALTERTABLE[tablename]REPLICAIDENTITYFULL;批量表操作通过代码块的方式，对某个schema中的所有表一起更新其复制标识。SELECTtablename,CASErelreplidentWHEN'd'TH
  • nosql数据库技术与应用知识点 皆过客，揽星河 NoSQLnosql数据库大数据数据分析数据结构非关系型数据库
    Nosql知识回顾大数据处理流程数据采集(flume、爬虫、传感器)数据存储(本门课程NoSQL所处的阶段)Hdfs、MongoDB、HBase等数据清洗(入仓)Hive等数据处理、分析(Spark、Flink等)数据可视化数据挖掘、机器学习应用(Python、SparkMLlib等)大数据时代存储的挑战(三高)高并发(同一时间很多人访问)高扩展(要求随时根据需求扩展存储)高效率(要求读写速度快)
  • SpringBlade dict-biz/list 接口 SQL 注入漏洞 文章永久免费只为良心 oracle数据库
    SpringBladedict-biz/list接口SQL注入漏洞POC:构造请求包查看返回包你的网址/api/blade-system/dict-biz/list?updatexml(1,concat(0x7e,md5(1),0x7e),1)=1漏洞概述在SpringBlade框架中，如果dict-biz/list接口的后台处理逻辑没有正确地对用户输入进行过滤或参数化查询（PreparedSta
  • insert into select 主键自增_mybatis拦截器实现主键自动生成 weixin_39521651 insertintoselect主键自增mybatisdelete返回值mybatisinsert返回主键mybatisinsert返回对象mybatisplusinsert返回主键mybatisplus插入生成id
    前言前阵子和朋友聊天，他说他们项目有个需求，要实现主键自动生成，不想每次新增的时候，都手动设置主键。于是我就问他，那你们数据库表设置主键自动递增不就得了。他的回答是他们项目目前的id都是采用雪花算法来生成，因此为了项目稳定性，不会切换id的生成方式。朋友问我有没有什么实现思路，他们公司的orm框架是mybatis，我就建议他说，不然让你老大把mybatis切换成mybatis-plus。mybat
  • 关于Mysql 中 Row size too large (＞ 8126) 错误的解决和理解 秋刀prince mysqlmysql数据库
    提示：啰嗦一嘴，数据库的任何操作和验证前，一定要记得先备份！！！不会有错；文章目录问题发现一、问题导致的可能原因1、页大小2、行格式2.1compact格式2.2Redundant格式2.3Dynamic格式2.4Compressed格式3、BLOB和TEXT列二、解决办法1、修改页大小（不推荐）2、修改行格式3、修改数据类型为BLOB和TEXT列4、其他优化方式（可以参考使用）4.1合理设置数据
  • Java爬虫框架（一）--架构设计 狼图腾-狼之传说 java框架java任务html解析器存储电子商务
    一、架构图那里搜网络爬虫框架主要针对电子商务网站进行数据爬取，分析，存储，索引。爬虫：爬虫负责爬取，解析，处理电子商务网站的网页的内容数据库：存储商品信息索引：商品的全文搜索索引Task队列：需要爬取的网页列表Visited表：已经爬取过的网页列表爬虫监控平台：web平台可以启动，停止爬虫，管理爬虫，task队列，visited表。二、爬虫1.流程1)Scheduler启动爬虫器，TaskMast
  • MongoDB知识概括 GeorgeLin98 持久层mongodb
    MongoDB知识概括MongoDB相关概念单机部署基本常用命令索引-IndexSpirngDataMongoDB集成副本集分片集群安全认证MongoDB相关概念业务应用场景：传统的关系型数据库（如MySQL），在数据操作的“三高”需求以及应对Web2.0的网站需求面前，显得力不从心。解释：“三高”需求：①Highperformance-对数据库高并发读写的需求。②HugeStorage-对海量数
  • Mongodb Error: queryTxt ETIMEOUT xxxx.wwwdz.mongodb.net 佛一脚 errorreactmongodb数据库
    背景每天都能遇到奇怪的问题，做个记录，以便有缘人能得到帮助！换了一台电脑开发nextjs程序。需要连接mongodb数据，对数据进行增删改查。上一台电脑好好的程序，新电脑死活连不上mongodb数据库。同一套代码，没任何修改，搞得我怀疑人生了，打开浏览器进入mongodb官网毫无问题，也能进入线上系统查看数据，网络应该是没问题。于是我尝试了一下手机热点，这次代码能正常跑起来，连接数据库了！！！是不
  • JAVA·一个简单的登录窗口 MortalTom java开发语言学习
    文章目录概要整体架构流程技术名词解释技术细节资源概要JavaSwing是Java基础类库的一部分，主要用于开发图形用户界面（GUI）程序整体架构流程新建项目，导入sql.jar包（链接放在了文末），编译项目并运行技术名词解释一、特点丰富的组件提供了多种可视化组件，如按钮（JButton）、文本框（JTextField）、标签（JLabel）、下拉列表（JComboBox）等，可以满足不同的界面设计
  • 入门MySQL——查询语法练习 K_un
    前言：前面几篇文章为大家介绍了DML以及DDL语句的使用方法，本篇文章将主要讲述常用的查询语法。其实MySQL官网给出了多个示例数据库供大家实用查询，下面我们以最常用的员工示例数据库为准，详细介绍各自常用的查询语法。1.员工示例数据库导入官方文档员工示例数据库介绍及下载链接：https://dev.mysql.com/doc/employee/en/employees-installation.h
  • 博客网站制作教程 2401_85194651 javamaven
    首先就是技术框架：后端：Java+SpringBoot数据库：MySQL前端：Vue.js数据库连接：JPA(JavaPersistenceAPI)1.项目结构blog-app/├──backend/│├──src/main/java/com/example/blogapp/││├──BlogApplication.java││├──config/│││└──DatabaseConfig.java
  • ubuntu安装wordpress lissettecarlr
    1安装nginx网上安装方式很多，这就就直接用apt-get了apt-getinstallnginx不用启动啥，然后直接在浏览器里面输入IP:80就能看到nginx的主页了。如果修改了一些配置可以使用下列命令重启一下systemctlrestartnginx.service2安装mysql输入安装前也可以更新一下软件源，在安装过程中将会让你输入数据库的密码。sudoapt-getinstallmy
  • 深入浅出 -- 系统架构之负载均衡Nginx的性能优化 xiaoli8748_软件开发 系统架构系统架构负载均衡nginx
    一、Nginx性能优化到这里文章的篇幅较长了，最后再来聊一下关于Nginx的性能优化，主要就简单说说收益最高的几个优化项，在这块就不再展开叙述了，毕竟影响性能都有多方面原因导致的，比如网络、服务器硬件、操作系统、后端服务、程序自身、数据库服务等，对于性能调优比较感兴趣的可以参考之前《JVM性能调优》中的调优思想。优化一：打开长连接配置通常Nginx作为代理服务，负责分发客户端的请求，那么建议开启H
  • 【RabbitMQ 项目】服务端：数据管理模块之绑定管理 月夜星辉雪 rabbitmq分布式
    文章目录一.编写思路二.代码实践一.编写思路定义绑定信息类交换机名称队列名称绑定关键字：交换机的路由交换算法中会用到没有是否持久化的标志，因为绑定是否持久化取决于交换机和队列是否持久化，只有它们都持久化时绑定才需要持久化。绑定就好像一根绳子，两端连接着交换机和队列，当一方不存在，它就没有存在的必要了定义绑定持久化类构造函数：如果数据库文件不存在则创建，打开数据库，创建binding_table插入
  • 计算机毕业设计PHP仓储综合管理系统（源码+程序+VUE+lw+部署） java毕设程序源码王哥 php课程设计vue.js
    该项目含有源码、文档、程序、数据库、配套开发软件、软件安装教程。欢迎交流项目运行环境配置：phpStudy+Vscode+Mysql5.7+HBuilderX+Navicat11+Vue+Express。项目技术：原生PHP++Vue等等组成，B/S模式+Vscode管理+前后端分离等等。环境需要1.运行环境：最好是小皮phpstudy最新版，我们在这个版本上开发的。其他版本理论上也可以。2.开发
  • MyBatis 详解 阿贾克斯的黎明 javamybatis
    目录目录一、MyBatis是什么二、为什么使用MyBatis（一）灵活性高（二）性能优化（三）易于维护三、怎么用MyBatis（一）添加依赖（二）配置MyBatis（三）创建实体类和接口（四）使用MyBatis一、MyBatis是什么MyBatis是一个优秀的持久层框架，它支持自定义SQL、存储过程以及高级映射。MyBatis免除了几乎所有的JDBC代码以及设置参数和获取结果集的工作。它可以通过简
  • 3.增删改查--连接查询 问女何所忆
    关系型数据库的一个特点就是，多张表之间存在关系，以致于我们可以连接多张表进行查询操作，所以连接查询会是关系型数据库中最常见的操作。连接查询主要分为三种，交叉连接、内连接和外连接，我们一个个说。1、交叉连接交叉连接其实连接查询的第一个阶段，它简单表现为两张表的笛卡尔积形式，具体例子：如果你没学过数学中的笛卡尔积概念，你可以这样简单的理解这里的交叉连接：两张表的交叉连接就是一个连接合并的过程，T1表中
  • You have an error in your SQL syntax； check the manual that corresponds to your MySQL server version 努力的菜鸟~ sql数据库
    YouhaveanerrorinyourSQLsyntax;checkthemanualthatcorrespondstoyourMySQLserverversionfortherightsyntaxtousenear‘IDENTIFIEDBY‘123456’WITHGRANTOPTION’atline1在mysql5.7之前GRANTALLPRIVILEGESON*.*TO'root'@'%'I
  • docker from指令的含义_多个FROM-含义 weixin_39722188 dockerfrom指令的含义
    小编典典什么是基本图片？一组文件，加上EXPOSE端口ENTRYPOINT和CMD。您可以添加文件并基于该基础图像构建新图像，Dockerfile并以FROM指令开头：后面提到的图像FROM是新图像的“基础图像”。这是否意味着如果我neo4j/neo4j在FROM指令中声明，则在运行映像时，neo数据库将自动运行并且可在端口7474的容器中使用？仅当您不覆盖CMD和时ENTRYPOINT。但是图像
  • Redis:缓存击穿 我的程序快快跑啊 缓存redisjava
    缓存击穿(热点key)：部分key(被高并发访问且缓存重建业务复杂的)失效,无数请求会直接到数据库，造成巨大压力1.互斥锁：可以保证强一致性线程一：未命中之后，获取互斥锁，再查询数据库重建缓存，写入缓存，释放锁线程二：查询未命中，未获得锁(已由线程一获得)，等待一会，缓存命中互斥锁实现方式：redis中setnxkeyvalue:改变对应key的value,仅当value不存在时执行，以此来实现互
  • mysql学习教程，从入门到精通，TOP 和MySQL LIMIT 子句（15） 知识分享小能手 大数据数据库MySQLmysql学习oracle数据库开发语言adb大数据
    1、TOP和MySQLLIMIT子句内容在SQL中，不同的数据库系统对于限制查询结果的数量有不同的实现方式。TOP关键字主要用于SQLServer和Access数据库中，而LIMIT子句则主要用于MySQL、PostgreSQL（通过LIMIT/OFFSET语法）、SQLite等数据库中。下面将分别详细介绍这两个功能的语法、语句以及案例。1.1、TOP子句（SQLServer和Access）1.1
  • ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your †徐先森® Oracle数据库Web相关错误集
    createtablestudents(idintunsignedprimarykeyauto_increment,namevarchar(50)notnull,ageintunsigned,highdecimal(3,2),genderenum('男','女','中性','保密','妖')default'保密',cls_idintunsigned);在对数据库插入如上带有中文带有默认值的字段的时
  • java杨辉三角 3213213333332132 java基础
    package com.algorithm; /** * @Description 杨辉三角 * @author FuJianyong * 2015-1-22上午10:10:59 */ public class YangHui { public static void main(String[] args) { //初始化二维数组长度 int[][] y
  • 《大话重构》之大布局的辛酸历史 白糖_ 重构
    《大话重构》中提到“大布局你伤不起”，如果企图重构一个陈旧的大型系统是有非常大的风险，重构不是想象中那么简单。我目前所在公司正好对产品做了一次“大布局重构”，下面我就分享这个“大布局”项目经验给大家。   背景         公司专注于企业级管理产品软件，企业有大中小之分，在2000年初公司用JSP/Servlet开发了一套针对中
  • 电驴链接在线视频播放源码 dubinwei 源码电驴播放器视频ed2k
    本项目是个搜索电驴（ed2k）链接的应用,借助于磁力视频播放器（官网： http://loveandroid.duapp.com/ 开放平台），可以实现在线播放视频，也可以用迅雷或者其他下载工具下载。 项目源码： http://git.oschina.net/svo/Emule,动态更新。也可从附件中下载。 项目源码依赖于两个库项目，库项目一链接： http://git.oschina.
  • Javascript中函数的toString()方法 周凡杨 JavaScriptjstoStringfunctionobject
    简述     The toString() method returns a string representing the source code of the function.     简译之，Javascript的toString()方法返回一个代表函数源代码的字符串。 句法     function.
  • struts处理自定义异常 g21121 struts
    很多时候我们会用到自定义异常来表示特定的错误情况，自定义异常比较简单，只要分清是运行时异常还是非运行时异常即可，运行时异常不需要捕获，继承自RuntimeException，是由容器自己抛出，例如空指针异常。 非运行时异常继承自Exception，在抛出后需要捕获，例如文件未找到异常。 此处我们用的是非运行时异常，首先定义一个异常LoginException: /** * 类描述：登录相
  • Linux中find常见用法示例 510888780 linux
    Linux中find常见用法示例 ·find   path   -option   [   -print ]   [ -exec   -ok   command ]   {} \; find命令的参数；
  • SpringMVC的各种参数绑定方式 Harry642 springMVC绑定表单
    1. 基本数据类型(以int为例，其他类似)： Controller代码： @RequestMapping("saysth.do") public void test(int count) { } 表单代码： <form action="saysth.do" method="post&q
  • Java 获取Oracle ROWID aijuans javaoracle
    A ROWID is an identification tag unique for each row of an Oracle Database table. The ROWID can be thought of as a virtual column, containing the ID for each row. The oracle.sql.ROWID class i
  • java获取方法的参数名 antlove javajdkparametermethodreflect
    reflect.ClassInformationUtil.java package reflect; import javassist.ClassPool; import javassist.CtClass; import javassist.CtMethod; import javassist.Modifier; import javassist.bytecode.CodeAtt
  • JAVA正则表达式匹配 查找 替换 提取操作 百合不是茶 java正则表达式替换提取查找
    正则表达式的查找;主要是用到String类中的split();       String str;      str.split();方法中传入按照什么规则截取,返回一个String数组   常见的截取规则: str.split("\\.")按照.来截取 str.
  • Java中equals()与hashCode()方法详解 bijian1013 javasetequals()hashCode()
    一.equals()方法详解     equals()方法在object类中定义如下：  public boolean equals(Object obj) { return (this == obj); }    很明显是对两个对象的地址值进行的比较（即比较引用是否相同）。但是我们知道，String 、Math、I
  • 精通Oracle10编程SQL(4)使用SQL语句 bijian1013 oracle数据库plsql
    --工资级别表 create table SALGRADE ( GRADE NUMBER(10), LOSAL NUMBER(10,2), HISAL NUMBER(10,2) ) insert into SALGRADE values(1,0,100); insert into SALGRADE values(2,100,200); inser
  • 【Nginx二】Nginx作为静态文件HTTP服务器 bit1129 HTTP服务器
     Nginx作为静态文件HTTP服务器 在本地系统中创建/data/www目录，存放html文件(包括index.html) 创建/data/images目录，存放imags图片 在主配置文件中添加http指令   http { server { listen 80; server_name
  • kafka获得最新partition offset blackproof kafkapartitionoffset最新
    kafka获得partition下标，需要用到kafka的simpleconsumer   import java.util.ArrayList; import java.util.Collections; import java.util.Date; import java.util.HashMap; import java.util.List; import java.
  • centos 7安装docker两种方式 ronin47
          第一种是采用yum 方式              yum install -y docker           
  • java-60-在O(1)时间删除链表结点 bylijinnan java
    public class DeleteNode_O1_Time { /** * Q 60 在O(1)时间删除链表结点 * 给定链表的头指针和一个结点指针(!!)，在O(1)时间删除该结点 * * Assume the list is: * head->...->nodeToDelete->mNode->nNode->..
  • nginx利用proxy_cache来缓存文件 cfyme cache
    user  zhangy users; worker_processes 10; error_log  /var/vlogs/nginx_error.log  crit; pid        /var/vlogs/nginx.pid; #Specifies the value for ma
  • [JWFD开源工作流]JWFD嵌入式语法分析器负号的使用问题 comsci 嵌入式
        假如我们需要用JWFD的语法分析模块定义一个带负号的方程式，直接在方程式之前添加负号是不正确的，而必须这样做：     string str01 = "a=3.14;b=2.71;c=0;c-((a*a)+(b*b))"     定义一个0整数c,然后用这个整数c去
  • 如何集成支付宝官方文档 dai_lm android
    官方文档下载地址 https://b.alipay.com/order/productDetail.htm?productId=2012120700377310&tabId=4#ps-tabinfo-hash 集成的必要条件 1. 需要有自己的Server接收支付宝的消息 2. 需要先制作app，然后提交支付宝审核，通过后才能集成 调试的时候估计会真的扣款，请注意
  • 应该在什么时候使用Hadoop datamachine hadoop
    原帖地址：http://blog.chinaunix.net/uid-301743-id-3925358.html 存档，某些观点与我不谋而合，过度技术化不可取，且hadoop并非万能。 --------------------------------------------万能的分割线-------------------------------- 有人问我，“你在大数据和Hado
  • 在GridView中对于有外键的字段使用关联模型进行搜索和排序 dcj3sjt126com yii
    在GridView中使用关联模型进行搜索和排序 首先我们有两个模型它们直接有关联: class Author extends CActiveRecord { ... } class Post extends CActiveRecord { ... function relations() { return array( '
  • 使用NSString 的格式化大全 dcj3sjt126com Objective-C
    格式定义The format specifiers supported by the NSString formatting methods and CFString formatting functions follow the IEEE printf specification; the specifiers are summarized in Table 1. Note that you c
  • 使用activeX插件对象object滚动有重影 蕃薯耀 activeX插件滚动有重影
      使用activeX插件对象object滚动有重影   <object style="width:0;" id="abc" classid="CLSID:D3E3970F-2927-9680-BBB4-5D0889909DF6" codebase="activex/OAX339.CAB#
  • SpringMVC4零配置 hanqunfeng springmvc4
    基于Servlet3.0规范和SpringMVC4注解式配置方式，实现零xml配置，弄了个小demo，供交流讨论。     项目说明如下： 1.db.sql是项目中用到的表，数据库使用的是oracle11g 2.该项目使用mvn进行管理，私服为自搭建nexus,项目只用到一个第三方 jar，就是oracle的驱动； 3.默认项目为零配置启动，如果需要更改启动方式，请
  • 《开源框架那点事儿16》：缓存相关代码的演变 j2eetop 开源框架
    问题引入 上次我参与某个大型项目的优化工作，由于系统要求有比较高的TPS，因此就免不了要使用缓冲。 该项目中用的缓冲比较多，有MemCache，有Redis，有的还需要提供二级缓冲，也就是说应用服务器这层也可以设置一些缓冲。 当然去看相关实现代代码的时候，大致是下面的样子。 [java] view plain copy print ? public vo
  • AngularJS浅析 kvhur JavaScript
    概念 AngularJS is a structural framework for dynamic web apps. 了解更多详情请见原文链接：http://www.gbtags.com/gb/share/5726.htm Directive 扩展html，给html添加声明语句，以便实现自己的需求。对于页面中html元素以ng为前缀的属性名称，ng是angular的命名空间
  • 架构师之jdk的bug排查(一)---------------split的点号陷阱 nannan408 split
    1.前言.    jdk1.6的lang包的split方法是有bug的,它不能有效识别A.b.c这种类型,导致截取长度始终是0.而对于其他字符,则无此问题.不知道官方有没有修复这个bug. 2.代码 String[] paths = "object.object2.prop11".split("'"); System.ou
  • 如何对10亿数据量级的mongoDB作高效的全表扫描 quentinXXZ mongodb
      本文链接:  http://quentinXXZ.iteye.com/blog/2149440 一、正常情况下，不应该有这种需求 首先，大家应该有个概念，标题中的这个问题，在大多情况下是一个伪命题，不应该被提出来。要知道，对于一般较大数据量的数据库，全表查询，这种操作一般情况下是不应该出现的，在做正常查询的时候，如果是范围查询，你至少应该要加上limit。 说一下，
  • C语言算法之水仙花数 qiufeihu c算法
    /** * 水仙花数 */ #include <stdio.h> #define N 10 int main() { int x,y,z; for(x=1;x<=N;x++) for(y=0;y<=N;y++) for(z=0;z<=N;z++) if(x*100+y*10+z == x*x*x
  • JSP指令 wyzuomumu jsp
    jsp指令的一般语法格式： <%@ 指令名 属性 =”值 ” %> 常用的三种指令： page,include,taglib page指令语法形式： <%@ page 属性 1=”值 1” 属性 2=”值 2”%> include指令语法形式： <%@include file=”relative url”%> (jsp可以通过 include
按字母分类： ABCDEFGHIJKLMNOPQRSTUVWXYZ其他