（mysql）DML语句 总结

DML ---数据操作语言（Data Manipulation Language)( insert delete update      插入  删除   更新)

DQL---- 数据查询语言（Data Query Language）(select  查询 )

插入修改数据

#如果每个字段都有值，不需要写字段名称,每组值用,隔开

mysql>INSERT INTO tb_name (col1,col2) VALUES ('STRING',NUM),('STRING',NUM); mysql>INSERT INTO tb_name SET col1='string',col2='string'; mysql>INSERT INTO tb_name (col1,col2,col3) SELECT...;

EXAMPLE:

1 2	mysql> INSERT INTO students ( Name ,Gender,teacher) VALUE ( 'lujunyi' , 'M' , 'mage' ),( 'wusong' , 'M' , 'zhuima' ); mysql> INSERT INTO students SET Name = 'lujunyi' ,Gender= 'M' ,tearcher= 'zhuima' ;

更新数据

1 2	mysql> UPDATE tb_name SET column =value WHERE column =value; mysql> UPDATE students SET Course= 'mysql' WHERE Name = 'lujunyi' ;

替换数据：

和UPDATE使用方式一样,只要将UPDATE换成REPLACE即可

删除数据

mysql>DELETE FROM tb_name WHERE conditions;//条件

单表查询： 

mysql>SELECT [DISTINCT] column FROM tb_name WHERE CONDITION; //DISTINCT在count计算不重复的记录的时候能用到 //比如SELECT COUNT( DISTINCT player_id ) FROM task; //就是计算talbebname表中id不同的记录有多少条

#重复的结果只显示一次

mysql> SELECT  DISTINCT  Gender  FROM  students;

#组合条件,可以使用AND,OR,NOT,XOR组合多个条件

mysql> SELECT  *  FROM  students  WHERE  Age>20  AND  Gender= 'M' ;

#使用BETWEEN...AND...筛选出年龄介于20-25之间的数据

mysql> SELECT  *  FROM  students  WHERE  Age  BETWEEN  20  AND  25;

#查询Name以Y开头的的数据，%表示任意长度的任意字符，_表示任意单个字符

mysql> SELECT  *  FROM  student  WHERE  Name  LIKE  'Y%' ;

使用IN关键词，将条件限定在一个列表中。用IS关键词，表示条件是否为空（IS NULL 或者 IS NOT NULL）

mysql> SELECT  *  FROM  students  WHERE  Age  IN  (20,22,24);

#将查询的结果进行排序

mysql> SELECT  *  FROM  students  ORDER  BY  Name  { ASC | DESC };

#查询结果别名显示

mysql> SELECT  Name  AS  Stu_Name  FROM  students;

#LIMIT限定查询结果的条数,LIMIT 2,3表示偏移2条数据后，取3条数据

mysql> SELECT  *  FROM  students LIMIT 2;

#求平均数:AVG()，最大值:MAX() 最小值MIN() 数量:COUNT() 求和:SUM()

mysql> SELECT  AVG (age)  FROM  students;

#分组GROUP BY

mysql> SELECT  Age, Gender  FROM  students  GROUP  BY  Gender;

#过滤:HAVING

mysql> SELECT  COUNT (Age)  AS  Num,Age  FROM  students  GROUP  BY  Age  HAVING  Num>2;

多表查询: 

#指定已哪个字段连接2张表

mysql> SELECT  students. Name ,courses.Cname  FROM  students,courses  WHERE  students.CID1 = courses.CID;

#左外连接...LEFT JION...ON...

mysql> SELECT  s. Name ,c.Cname  FROM  students  AS  s  LEFT  JION courses  AS  c  ON  s.CID1=c.CID;

#右外连接...RIGHT JION...ON...

mysql> SELECT  s. Name ,c.Cname  FROM  students  AS  s  RIGHT  JION courses  AS  c  ON  s.CID1=c.CID;

子查询

#查询年龄大于平均年龄的数据

mysql> SELECT  *  FROM  students  WHERE  Age > ( SELECT  AVG (Age)  FROM  students);

#在FROM中使用子查询

mysql> SELECT  Name ,Age  FROM  ( SELECT  *  FROM  students  WHERE  CID  IN  (2,3))  AS  t  WHERE  Age>20;

#联合查询

mysql>( SELECT  Name ,Age  FROM  students)  UNION  ( SELECT  Tname,Age  FROM  tutors);