• 2014.9.3数据库CRUD


    CRUD 增删改查

     

    DCL 数据控制语言:备份,grant

    DML 数据操作语言: CRUD

    DDL 数据定义语言:create drop alter 

     

    自增长列不能赋值

    增:

    Insert into 表名 values‘’,’’,’’,’’,’’)--into可以省略

    删:

    Delete from 表名(有日志)(慢)   truncate table 表名(不写日志,下次执行自增长列从1开始)(快)

    Delete from 表 where 列名 关系运算符 值

    改:

    Update 表 from set 列名=值,列名=值,......where 列名 关系运算符 值

    查:

    Select * from 

    Select 列名,列名,......  From 

    Select * from 表 where 列名 关系运算符 值 and 列名 关系运算符 值

    Select * from 表 where 列 between 10 and 20 (范围查询)

    Select * from 列 where 列 in 3,4,5

    Select  distinct 列 from 表  (列去重)

    Select * from car where name like  %5%     %任意多个任意字符;_一个任意字符

    对列的筛选——投影

    对行的筛选——筛选

    行——记录(元组) 列——字段(属性)

     

     1 select * from Fruit
     2 select * from Fruit where Stack in (3,4,5)
     3 Select * from car where name like  '%5%'--通配符   %  _
     4 select * from car where name like '%型'
     5 select * from car where name like '宝%'
     6 select * from car where name like '%型'
     7 select * from car where name like '__[3,5]%'--中括号表示选其一
     8 --排序
     9 select * from car order by price     --升序
    10 select * from car order by price desc  --降序
    11 select * from car order by price,oil asc,exhaust desc
    12 select * from car where price>30 order by price
    13 --统计   5个
    14 select COUNT(*) from car where name like '奥迪%'--有多少个奥迪开头的记录
    15 select AVG(price) from car--统计car所有记录price的平均值
    16 select SUM(price/oil) from car
    17 select * ,(price*0.9) jiu折 from car
    18 select code 代号,name 名称 from car
    19 select MAX(price) from car
    20 select * from car where price in (select MIN(price) from car)--找出最小值所在的记录(行)
    21 
    22 --分组
    23 select oil,COUNT(*) from car group by oil order by COUNT(*)
    24 select oil,COUNT(*) from car where price>50 group by oil order by COUNT(*)
    25 select brand,MAX(price) from car group by brand
    26 select brand,Min(price) from car group by brand
    27 
    28 select oil,COUNT(*) from car group by oil having COUNT(*)>=2   --having分组后筛选
    29 --根据身份证号分组统计;筛选个数大于1
    30 select stack from Fruit group by Stack having COUNT(*)>1

     

     

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  • 原文地址:https://www.cnblogs.com/zsmj001/p/3956996.html
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