数据库语句说明

 ***SELECT***

select *(列名) from table_name(表名) where column_name operator value
ex:(宿主)
select * from stock_information where stockid = str(nid)
stockname = 'str_name'
stockname like '% find this %'
stockname like '[a-zA-Z]%' --------- ([]指定值的范围)
stockname like '[^F-M]%' --------- (^排除指定范围)
--------- 只能在使用like关键字的where子句中使用通配符)
or stockpath = 'stock_path'
or stocknumber < 1000
and stockindex = 24
not stocksex = 'man'
stocknumber between 20 and 100
stocknumber in(10,20,30)
order by stockid desc(asc) --------- 排序，desc-降序，asc-升序
order by 1,2 --------- by列号
stockname = (select stockname from stock_information where stockid = 4)
--------- 子查询
--------- 除非能确保内层select只返回一个行的值，
--------- 否则应在外层where子句中用一个in限定符
select distinct column_name form table_name --------- distinct指定检索独有的列值，不重复
select stocknumber ,"stocknumber + 10" = stocknumber + 10 from table_name
select stockname , "stocknumber" = count(*) from table_name group by stockname
--------- group by 将表按行分组,指定列中有相同的值
having count(*) = 2 --------- having选定指定的组

select *
from table1, table2
where table1.id *= table2.id -------- 左外部连接，table1中有的而table2中没有得以null表示
table1.id =* table2.id -------- 右外部连接

 

select stockname from table1
union [all] ----- union合并查询结果集，all-保留重复行
select stockname from table2

 

***insert***

 

insert into table_name (Stock_name,Stock_number) value ("xxx","xxxx")
value (select Stockname , Stocknumber from Stock_table2)---value为select语句

 

***update***

 

update table_name set Stockname = "xxx" [where Stockid = 3]
Stockname = default
Stockname = null
Stocknumber = Stockname + 4

 

***delete***

 

delete from table_name where Stockid = 3
truncate table_name ----------- 删除表中所有行，仍保持表的完整性
drop table table_name --------------- 完全删除表

 

***alter table*** --- 修改数据库表结构

 

alter table database.owner.table_name add column_name char(2) null .....
sp_help table_name ---- 显示表已有特征
create table table_name (name char(20), age smallint, lname varchar(30))
insert into table_name select ......... ----- 实现删除列的方法（创建新表）
alter table table_name drop constraint Stockname_default ---- 删除Stockname的default约束

***function(/*常用函数*/)***

 

----统计函数----
AVG --求平均值
COUNT --统计数目
MAX --求最大值
MIN --求最小值
SUM --求和

 

--AVG
use pangu
select avg(e_wage) as dept_avgWage from employee group by dept_id

 

--MAX
--求工资最高的员工姓名
use pangu
select e_name from employee where e_wage = (select max(e_wage) from employee)

 

转自bbs.kesion.com