高级查询在数据库中用得是最频繁的，也是应用最广泛的。
基本常用查询
--select select * from student; --all 查询所有 select all sex from student; --distinct 过滤重复 select distinct sex from student; --count 统计 select count(*) from student; select count(sex) from student; select count(distinct sex) from student; --top 取前N条记录 select top 3 * from student; --alias column name 列重命名 select id as 编号, name '名称', sex 性别 from student; --alias table name 表重命名 select id, name, s.id, s.name from student s; --column 列运算 select (age + id) col from student; select s.name + '-' + c.name from classes c, student s where s.cid = c.id; --where 条件 select * from student where id = 2; select * from student where id > 7; select * from student where id < 3; select * from student where id <> 3; select * from student where id >= 3; select * from student where id <= 5; select * from student where id !> 3; select * from student where id !< 5; --and 并且 select * from student where id > 2 and sex = 1; --or 或者 select * from student where id = 2 or sex = 1; --between ... and ... 相当于并且 select * from student where id between 2 and 5; select * from student where id not between 2 and 5; --like 模糊查询 select * from student where name like '%a%'; select * from student where name like '%[a][o]%'; select * from student where name not like '%a%'; select * from student where name like 'ja%'; select * from student where name not like '%[j,n]%'; select * from student where name like '%[j,n,a]%'; select * from student where name like '%[^ja,as,on]%'; select * from student where name like '%[ja_on]%'; --in 子查询 select * from student where id in (1, 2); --not in 不在其中 select * from student where id not in (1, 2); --is null 是空 select * from student where age is null; --is not null 不为空 select * from student where age is not null; --order by 排序 select * from student order by name; select * from student order by name desc; select * from student order by name asc; --group by 分组 按照年龄进行分组统计 select count(age), age from student group by age; 按照性别进行分组统计 select count(*), sex from student group by sex; 按照年龄和性别组合分组统计，并排序 select count(*), sex from student group by sex, age order by age; 按照性别分组，并且是id大于2的记录最后按照性别排序 select count(*), sex from student where id > 2 group by sex order by sex; 查询id大于2的数据，并完成运算后的结果进行分组和排序 select count(*), (sex * id) new from student where id > 2 group by sex * id order by sex * id; --group by all 所有分组 按照年龄分组，是所有的年龄 select count(*), age from student group by all age; --having 分组过滤条件 按照年龄分组，过滤年龄为空的数据，并且统计分组的条数和现实年龄信息 select count(*), age from student group by age having age is not null; 按照年龄和cid组合分组，过滤条件是cid大于1的记录 select count(*), cid, sex from student group by cid, sex having cid > 1; 按照年龄分组，过滤条件是分组后的记录条数大于等于2 select count(*), age from student group by age having count(age) >= 2; 按照cid和性别组合分组，过滤条件是cid大于1，cid的最大值大于2 select count(*), cid, sex from student group by cid, sex having cid > 1 and max(cid) > 2;
嵌套子查询
子查询是一个嵌套在select、insert、update或delete语句或其他子查询中的查询。任何允许使用表达式的地方都可以使用子查询。子查询也称为内部查询或内部选择，而包含子查询的语句也成为外部查询或外部选择。
from (select … table)示例
将一个table的查询结果当做一个新表进行查询
select * from (
select id, name from student where sex = 1
) t where t.id > 2;
上面括号中的语句，就是子查询语句（内部查询）。在外面的是外部查询，其中外部查询可以包含以下语句：
1、 包含常规选择列表组件的常规select查询
2、 包含一个或多个表或视图名称的常规from语句
3、 可选的where子句
4、 可选的group by子句
5、 可选的having子句
示例
查询班级信息，统计班级学生人生 select *, (select count(*) from student where cid = classes.id) as num from classes order by num;
in, not in子句查询示例
查询班级id大于小于的这些班级的学生信息
select * from student where cid in (
select id from classes where id > 2 and id < 4
);
查询不是班的学生信息
select * from student where cid not in (
select id from classes where name = '2班'
)
in、not in 后面的子句返回的结果必须是一列，这一列的结果将会作为查询条件对应前面的条件。如cid对应子句的id；
exists和not exists子句查询示例
查询存在班级id为的学生信息
select * from student where exists (
select * from classes where id = student.cid and id = 3
);
查询没有分配班级的学生信息
select * from student where not exists (
select * from classes where id = student.cid
);
exists和not exists查询需要内部查询和外部查询进行一个关联的条件，如果没有这个条件将是查询到的所有信息。如：id等于student.id；
some、any、all子句查询示例
select * from student where cid = 5 and age > all (
select age from student where cid = 3
);
select * from student where cid = 5 and age > any (
select age from student where cid = 3
);
select * from student where cid = 5 and age > some (
select age from student where cid = 3
);
聚合查询
1、 distinct去掉重复数据
select distinct sex from student; select count(sex), count(distinct sex) from student;
2、 compute和compute by汇总查询
对年龄大于的进行汇总 select age from student where age > 20 order by age compute sum(age) by age; 对年龄大于的按照性别进行分组汇总年龄信息 select id, sex, age from student where age > 20 order by sex, age compute sum(age) by sex; 按照年龄分组汇总 select age from student where age > 20 order by age, id compute sum(age); 按照年龄分组，年龄汇总，id找最大值 select id, age from student where age > 20 order by age compute sum(age), max(id);
compute进行汇总前面是查询的结果，后面一条结果集就是汇总的信息。compute子句中可以添加多个汇总表达式，可以添加的信息如下：
a、 可选by关键字。它是每一列计算指定的行聚合
b、 行聚合函数名称。包括sum、avg、min、max、count等
c、 要对其执行聚合函数的列
compute by适合做先分组后汇总的业务。compute by后面的列一定要是order by中出现的列。
3、 cube汇总
cube汇总和compute效果类似，但语法较简洁，而且返回的是一个结果集。
select count(*), sex from student group by sex with cube; select count(*), age, sum(age) from student where age is not null group by age with cube;
cube要结合group by语句完成分组汇总
排序函数
排序在很多地方需要用到，需要对查询结果进行排序并且给出序号。比如：
1、 对某张表进行排序，序号需要递增不重复的
2、 对学生的成绩进行排序，得出名次，名次可以并列，但名次的序号是连续递增的
3、 在某些排序的情况下，需要跳空序号，虽然是并列
基本语法
排序函数 over([分组语句] 排序子句[desc][asc]) 排序子句 order by 列名, 列名 分组子句 partition by 分组列, 分组列
row_number函数
根据排序子句给出递增连续序号
按照名称排序的顺序递增 select s.id, s.name, cid, c.name, row_number() over(order by c.name) as number from student s, classes c where cid = c.id;
rank函数函数
根据排序子句给出递增的序号，但是存在并列并且跳空
select id, name, rank() over(order by cid) as rank from student; 跳过相同递增 select s.id, s.name, cid, c.name, rank() over(order by c.name) as rank from student s, classes c where cid = c.id;
dense_rank函数
根据排序子句给出递增的序号，但是存在并列不跳空
不跳过，直接递增 select s.id, s.name, cid, c.name, dense_rank() over(order by c.name) as dense from student s, classes c where cid = c.id;
partition by分组子句
可以完成对分组的数据进行增加排序，partition by可以与以上三个函数联合使用。
利用partition by按照班级名称分组，学生id排序 select s.id, s.name, cid, c.name, row_number() over(partition by c.name order by s.id) as rank from student s, classes c where cid = c.id; select s.id, s.name, cid, c.name, rank() over(partition by c.name order by s.id) as rank from student s, classes c where cid = c.id; select s.id, s.name, cid, c.name, dense_rank() over(partition by c.name order by s.id) as rank from student s, classes c where cid = c.id;
ntile平均排序函数
将要排序的数据进行平分，然后按照等分排序。ntile中的参数代表分成多少等分。
select s.id, s.name, cid, c.name, ntile(5) over(order by c.name) as ntile from student s, classes c where cid = c.id;
集合运算
操作两组查询结果，进行交集、并集、减集运算
1、 union和union all进行并集运算
--union 并集、不重复 select id, name from student where name like 'ja%' union select id, name from student where id = 4; --并集、重复 select * from student where name like 'ja%' union all select * from student;
2、 intersect进行交集运算
--交集（相同部分） select * from student where name like 'ja%' intersect select * from student;
3、 except进行减集运算
--减集（除相同部分） select * from student where name like 'ja%' except select * from student where name like 'jas%';
公式表表达式
查询表的时候，有时候中间表需要重复使用，这些子查询被重复查询调用，不但效率低，而且可读性低，不利于理解。那么公式表表达式可以解决这个问题。
我们可以将公式表表达式（CET）视为临时结果集，在select、insert、update、delete或是create view语句的执行范围内进行定义。
--表达式
with statNum(id, num) as
(
select cid, count(*)
from student
where id > 0
group by cid
)
select id, num from statNum order by id;
with statNum(id, num) as
(
select cid, count(*)
from student
where id > 0
group by cid
)
select max(id), avg(num) from statNum;
连接查询
1、 简化连接查询
--简化联接查询 select s.id, s.name, c.id, c.name from student s, classes c where s.cid = c.id;
2、 left join左连接
--左连接 select s.id, s.name, c.id, c.name from student s left join classes c on s.cid = c.id;
3、 right join右连接
--右连接 select s.id, s.name, c.id, c.name from student s right join classes c on s.cid = c.id;
4、 inner join内连接
--内连接 select s.id, s.name, c.id, c.name from student s inner join classes c on s.cid = c.id; --inner可以省略 select s.id, s.name, c.id, c.name from student s join classes c on s.cid = c.id;
5、 cross join交叉连接
5、 cross join交叉连接 --交叉联接查询，结果是一个笛卡儿乘积 select s.id, s.name, c.id, c.name from student s cross join classes c --where s.cid = c.id;
6、 自连接（同一张表进行连接查询）
--自连接 select distinct s.* from student s, student s1 where s.id <> s1.id and s.sex = s1.sex;
函数
1、 聚合函数
max最大值、min最小值、count统计、avg平均值、sum求和、var求方差
select
max(age) max_age,
min(age) min_age,
count(age) count_age,
avg(age) avg_age,
sum(age) sum_age,
var(age) var_age
from student;
2、 日期时间函数
select dateAdd(day, 3, getDate());--加天
select dateAdd(year, 3, getDate());--加年
select dateAdd(hour, 3, getDate());--加小时
--返回跨两个指定日期的日期边界数和时间边界数
select dateDiff(day, '2011-06-20', getDate());
--相差秒数
select dateDiff(second, '2011-06-22 11:00:00', getDate());
--相差小时数
select dateDiff(hour, '2011-06-22 10:00:00', getDate());
select dateName(month, getDate());--当前月份
select dateName(minute, getDate());--当前分钟
select dateName(weekday, getDate());--当前星期
select datePart(month, getDate());--当前月份
select datePart(weekday, getDate());--当前星期
select datePart(second, getDate());--当前秒数
select day(getDate());--返回当前日期天数
select day('2011-06-30');--返回当前日期天数
select month(getDate());--返回当前日期月份
select month('2011-11-10');
select year(getDate());--返回当前日期年份
select year('2010-11-10');
select getDate();--当前系统日期
select getUTCDate();--utc日期
3、 数学函数
select pi();--PI函数 select rand(100), rand(50), rand(), rand();--随机数 select round(rand(), 3), round(rand(100), 5);--精确小数位 --精确位数，负数表示小数点前 select round(123.456, 2), round(254.124, -2); select round(123.4567, 1, 2);
4、 元数据
select col_name(object_id('student'), 1);--返回列名
select col_name(object_id('student'), 2);
--该列数据类型长度
select col_length('student', col_name(object_id('student'), 2));
--该列数据类型长度
select col_length('student', col_name(object_id('student'), 1));
--返回类型名称、类型id
select type_name(type_id('varchar')), type_id('varchar');
--返回列类型长度
select columnProperty(object_id('student'), 'name', 'PRECISION');
--返回列所在索引位置
select columnProperty(object_id('student'), 'sex', 'ColumnId');
5、 字符串函数
select ascii('a');--字符转换ascii值
select ascii('A');
select char(97);--ascii值转换字符
select char(65);
select nchar(65);
select nchar(45231);
select nchar(32993);--unicode转换字符
select unicode('A'), unicode('中');--返回unicode编码值
select soundex('hello'), soundex('world'), soundex('word');
select patindex('%a', 'ta'), patindex('%ac%', 'jack'), patindex('dex%', 'dexjack');--匹配字符索引
select 'a' + space(2) + 'b', 'c' + space(5) + 'd';--输出空格
select charIndex('o', 'hello world');--查找索引
select charIndex('o', 'hello world', 6);--查找索引
select quoteName('abc[]def'), quoteName('123]45');
--精确数字
select str(123.456, 2), str(123.456, 3), str(123.456, 4);
select str(123.456, 9, 2), str(123.456, 9, 3), str(123.456, 6, 1), str(123.456, 9, 6);
select difference('hello', 'helloWorld');--比较字符串相同
select difference('hello', 'world');
select difference('hello', 'llo');
select difference('hello', 'hel');
select difference('hello', 'hello');
select replace('abcedef', 'e', 'E');--替换字符串
select stuff('hello world', 3, 4, 'ABC');--指定位置替换字符串
select replicate('abc#', 3);--重复字符串
select subString('abc', 1, 1), subString('abc', 1, 2), subString('hello Wrold', 7, 5);--截取字符串
select len('abc');--返回长度
select reverse('sqlServer');--反转字符串
select left('leftString', 4);--取左边字符串
select left('leftString', 7);
select right('leftString', 6);--取右边字符串
select right('leftString', 3);
select lower('aBc'), lower('ABC');--小写
select upper('aBc'), upper('abc');--大写
--去掉左边空格
select ltrim(' abc'), ltrim('# abc#'), ltrim(' abc');
--去掉右边空格
select rtrim(' abc '), rtrim('# abc# '), rtrim('abc');
6、 安全函数
select current_user;
select user;
select user_id(), user_id('dbo'), user_id('public'), user_id('guest');
select user_name(), user_name(1), user_name(0), user_name(2);
select session_user;
select suser_id('sa');
select suser_sid(), suser_sid('sa'), suser_sid('sysadmin'), suser_sid('serveradmin');
select is_member('dbo'), is_member('public');
select suser_name(), suser_name(1), suser_name(2), suser_name(3);
select suser_sname(), suser_sname(0x01), suser_sname(0x02), suser_sname(0x03);
select is_srvRoleMember('sysadmin'), is_srvRoleMember('serveradmin');
select permissions(object_id('student'));
select system_user;
select schema_id(), schema_id('dbo'), schema_id('guest');
select schema_name(), schema_name(1), schema_name(2), schema_name(3);
7、 系统函数
select app_name();--当前会话的应用程序名称
select cast(2011 as datetime), cast('10' as money), cast('0' as varbinary);--类型转换
select convert(datetime, '2011');--类型转换
select coalesce(null, 'a'), coalesce('123', 'a');--返回其参数中第一个非空表达式
select collationProperty('Traditional_Spanish_CS_AS_KS_WS', 'CodePage');
select current_timestamp;--当前时间戳
select current_user;
select isDate(getDate()), isDate('abc'), isNumeric(1), isNumeric('a');
select dataLength('abc');
select host_id();
select host_name();
select db_name();
select ident_current('student'), ident_current('classes');--返回主键id的最大值
select ident_incr('student'), ident_incr('classes');--id的增量值
select ident_seed('student'), ident_seed('classes');
select @@identity;--最后一次自增的值
select identity(int, 1, 1) as id into tab from student;--将studeng表的烈属，以/1自增形式创建一个tab
select * from tab;
select @@rowcount;--影响行数
select @@cursor_rows;--返回连接上打开的游标的当前限定行的数目
select @@error;--T-SQL的错误号
select @@procid;
8、 配置函数
set datefirst 7;--设置每周的第一天，表示周日 select @@datefirst as '星期的第一天', datepart(dw, getDate()) AS '今天是星期'; select @@dbts;--返回当前数据库唯一时间戳 set language 'Italian'; select @@langId as 'Language ID';--返回语言id select @@language as 'Language Name';--返回当前语言名称 select @@lock_timeout;--返回当前会话的当前锁定超时设置（毫秒） select @@max_connections;--返回SQL Server 实例允许同时进行的最大用户连接数 select @@MAX_PRECISION AS 'Max Precision';--返回decimal 和numeric 数据类型所用的精度级别 select @@SERVERNAME;--SQL Server 的本地服务器的名称 select @@SERVICENAME;--服务名 select @@SPID;--当前会话进程id select @@textSize; select @@version;--当前数据库版本信息
9、 系统统计函数
select @@CONNECTIONS;--连接数
select @@PACK_RECEIVED;
select @@CPU_BUSY;
select @@PACK_SENT;
select @@TIMETICKS;
select @@IDLE;
select @@TOTAL_ERRORS;
select @@IO_BUSY;
select @@TOTAL_READ;--读取磁盘次数
select @@PACKET_ERRORS;--发生的网络数据包错误数
select @@TOTAL_WRITE;--sqlserver执行的磁盘写入次数
select patIndex('%soft%', 'microsoft SqlServer');
select patIndex('soft%', 'software SqlServer');
select patIndex('%soft', 'SqlServer microsoft');
select patIndex('%so_gr%', 'Jsonisprogram');
10、 用户自定义函数
查看当前数据库所有函数
--查询所有已创建函数
select definition,* from sys.sql_modules m join sys.objects o on m.object_id = o.object_id
and type in('fn', 'if', 'tf');
创建函数
if (object_id('fun_add', 'fn') is not null)
drop function fun_add
go
create function fun_add(@num1 int, @num2 int)
returns int
with execute as caller
as
begin
declare @result int;
if (@num1 is null)
set @num1 = 0;
if (@num2 is null)
set @num2 = 0;
set @result = @num1 + @num2;
return @result;
end
go
调用函数
select dbo.fun_add(id, age) from student;
--自定义函数，字符串连接
if (object_id('fun_append', 'fn') is not null)
drop function fun_append
go
create function fun_append(@args nvarchar(1024), @args2 nvarchar(1024))
returns nvarchar(2048)
as
begin
return @args + @args2;
end
go
select dbo.fun_append(name, 'abc') from student;
# 修改函数
alter function fun_append(@args nvarchar(1024), @args2 nvarchar(1024))
returns nvarchar(1024)
as
begin
declare @result varchar(1024);
--coalesce返回第一个不为null的值
set @args = coalesce(@args, '');
set @args2 = coalesce(@args2, '');;
set @result = @args + @args2;
return @result;
end
go
select dbo.fun_append(name, '#abc') from student;
修改函数
alter function fun_append(@args nvarchar(1024), @args2 nvarchar(1024))
returns nvarchar(1024)
as
begin
declare @result varchar(1024);
--coalesce返回第一个不为null的值
set @args = coalesce(@args, '');
set @args2 = coalesce(@args2, '');;
set @result = @args + @args2;
return @result;
end
go
select dbo.fun_append(name, '#abc') from student;
返回table类型函数
--返回table对象函数
select name, object_id, type from sys.objects where type in ('fn', 'if', 'tf') or type like '%f%';
if (exists (select * from sys.objects where type in ('fn', 'if', 'tf') and name = 'fun_find_stuRecord'))
drop function fun_find_stuRecord
go
create function fun_find_stuRecord(@id int)
returns table
as
return (select * from student where id = @id);
go
select * from dbo.fun_find_stuRecord(2);
总结
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