SQL语句大全

查询数据：
select * from Task


*  代表整个表


单独查询*改成列名称  用半角,隔开


select * from Task where id=19  
 显示id为9的数据


select * from Task where taskStatus=1
查询taskStatus列的值为1的数据


select * from Task where taskName='导火线'
   数据库里面字符是用单引号


select * from Task where id=35 and taskName= '四儿'  and userID=1
     多个条件用and 或 or 连接


select id*2 from Task 
      所有的id都乘2


select * from Task  where id>9  
    查询id>9的所有数据(=     >    <     ! =     ! <     !>     <>)   <>为不等于


select * from Task  where id   between 19 and 24
      包括19和24


select * from Task  where id in(3,2,4,32,3,5)


--select * from Task  where id in(3,2,4,32,3,5)  --是备注


In(里面是字符串的话要加‘’)

select * from Task  where id is NULL     就这个NULL有这种用法

select * from Task  where taskName like '一%'   
     模糊查询，只查第一个字为一的，%表示后面的N个字...


select * from Task  where taskName like '一______'
        查第一个字为一，后面还有几个字就加几个下划线


select * from Task  where taskName like '%s_'
                 倒数第二个是s的数据


select * from Task  order by id (asc)  
      默认为升序


select * from Task  order by id desc
     降序


select * from Task where userID=1 order by id asc       --组合




select COUNT(*) from Task    查询一共有多少刚数据




select sum(id) from Task    求和


select sum(id) as 总数 from Task      得出的数取个名字叫  总数
              MAX()  MIN()  AVG()    用法同上                         数据库不区分大小写




select * from Task where userID=(select userID from UserInfo where userName ='admin')
     查询Task里面userID为UserInfo中userID的数据




insert into Task(taskName ,createTime,taskStatus,userID )
             values('sda','2009-08-09',1,2)
        插入 要一一对应
 
    delete (from) Task where taskName ='sda'

          删除


 update Task set userID=100 where id=32
          修改




select * from Reader where reader_ID in(select reader_ID from Borrow group by reader_ID having COUNT(book_ID)>2)




select * from Reader where reader_ID 
in(select reader_id from Borrow group by reader_ID having COUNT(book_ID)>2) 
and sex='女'


--错误，select book_ID from Borrow group by reader_ID 中book_ID的地方只能是reader_ID或者集合函数，
--只能返回一个值.
select * from Book where book_ID 
in(select book_ID from Borrow group by reader_ID having reader_ID =
(select reader_ID from Reader where name='施秋乐'))


--查找每个出版社介个最高的图书
select publish,name from Book a where price in
(select  max(price) from Book b where a.publish=b.publish)




--distinct去掉相同的reader_ID
select * from Reader  where reader_ID not in(select distinct reader_ID from Borrow)




--some[] 一部分值
--all[]  全部值


select * from Borrow join  Reader on Borrow.reader_ID=Reader.reader_ID where name='施秋乐'
--表的连接


select Reader.name as 读者姓名,Book.name as 图书名称,Borrow.borrowdate as 借阅时间 from Reader 
join Borrow on Reader.reader_ID=Borrow.reader_ID
join Book on Book.book_ID=Borrow.book_ID

with t(图书编号,借阅人数)
as
(select book_id as 图书编号,count(*) as 借阅人数
from borrow group by book_id)
select 图书编号 from t where 借阅人数=(select max(借阅人数) from t)


--with可以构造临时表....




Update 表名 set 列名=值,..... where 条件
update reader set name='hh' where id=1212