SQL Server SQL高级查询语句小结高级查询语句小结
Ø 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
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