mysql基本SQL语句
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SQL语句中的大小写问题
a.关键字、函数名、列名和索引名不区分大小写。
b.数据库名、表名、别名及视图名区分大小写。
一.基本的操作
1.库操作
mysql> show databases; #查看所有库 mysql> use mysql; #切换库 mysql> create database test_ku; #创建一个库 mysql> drop database test_ku; #删除一个库
2.表操作
mysql> show tables; #查看当前库中的所有列表
mysql> create table class_7(id int(11),name char(10),addr char(10)); #创建一个表
mysql> desc class_7; #查看表的结构
mysql> show create table student_info; #查看表的属性
mysql> show create table student_info\G
mysql> alter table class_7 rename to student_info; #更改表的名字
mysql> drop table student_info; #删除表
3.字段操作
mysql> alter table score add id int(2) first; #在最前面添加字段
mysql> alter table score add record int(3); #添加字段，默认最后添加
mysql> alter table score add sex char(3) after name; #在制定的字段后面添加字段
mysql> alter table score change record first_record int(2) default 0; #修改字段名和属性
mysql> alter table score modify sex enum(‘男‘,‘女‘); #修改字段属性的另一种方法，与change不同的是不能修改字段名
+--------------+-------------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------------+-------------------+------+-----+---------+-------+ | id | int(2) | YES | | NULL | | | name | char(4) | YES | | NULL | | | sex | enum(‘男‘,‘女‘) | YES | | NULL | | | first_record | int(2) | YES | | 0 | | +--------------+-------------------+------+-----+---------+-------+
mysql> alter table score drop first_record; #删除字段
4.记录操作（增删改）
（1）增（insert）
mysql> insert into score value(1,‘科比‘,‘男‘); #按照默认的顺序添加
mysql> insert into score(id,name) value(‘2‘,‘毛线‘); #也可以指定要添加的字段
mysql> insert into score value(4,‘蒋大爷‘,‘男‘),(5,‘秦子琪‘,‘女‘); #也可以一次添加多条
（2）改（update）
mysql> update score set sex = ‘男‘ where id = 2; #按照条件修改字段
（3）删（delete）
mysql> delete from score where id = ‘0‘; #指定条件删除
mysql> delete from t1 where name is null; #删除字段为空的那一行
mysql> delete from t1; #没有指定条件就会删除整张表
二、列表的查询方法
+----+--------+---------+--------------+-------+ | id | name | dorm | addr | score | +----+--------+---------+--------------+-------+ | 1 | 科比 | 6号楼 | 湖北罗田 | 67 | | 2 | 毛线 | 6号楼 | 湖北孝感 | 78 | | 3 | 黄鱼 | 5号楼 | 湖北罗田 | 75 | | 4 | 子豪 | 6号楼 | 江苏扬州 | 45 | | 5 | 星爷 | 5号楼 | 湖北孝感 | 1 | | 6 | 代鹏 | 5号楼 | 江苏盐城 | 85 | | 7 | 子栋 | 6号楼 | 湖北洪湖 | 95 | | 8 | 周攀 | 6号楼 | 湖北武穴 | 56 | | 9 | 大爷 | 5号楼 | 湖北通城 | 82 | | 10 | 小鸟 | 6号楼 | 湖北襄阳 | 38 | +----+--------+---------+--------------+-------+
（1）where
条件判断
mysql> select * from test_info where score < 60; #查询分数低于60分
+----+--------+---------+--------------+-------+ | id | name | dorm | addr | score | +----+--------+---------+--------------+-------+ | 4 | 子豪 | 6号楼 | 江苏扬州 | 45 | | 5 | 星爷 | 5号楼 | 湖北孝感 | 1 | | 8 | 周攀 | 6号楼 | 湖北武穴 | 56 | | 10 | 小鸟 | 6号楼 | 湖北襄阳 | 38 | +----+--------+---------+--------------+-------+
mysql> select * from test_info where score > 70 and addr = "湖北罗田"; #分数大于70，而且还是罗田的
mysql> select * from test_info where score > 70 and addr = "湖北罗田"; +----+--------+---------+--------------+-------+ | id | name | dorm | addr | score | +----+--------+---------+--------------+-------+ | 3 | 黄鱼 | 5号楼 | 湖北罗田 | 75 | +----+--------+---------+--------------+-------+ 1 row in set (0.00 sec)
mysql> select * from test_info where dorm = "5号楼" or score > 90; #分数大于90或者在5号楼住
mysql> select * from test_info where dorm = "5号楼" or score > 90; +----+--------+---------+--------------+-------+ | id | name | dorm | addr | score | +----+--------+---------+--------------+-------+ | 3 | 黄鱼 | 5号楼 | 湖北罗田 | 75 | | 5 | 星爷 | 5号楼 | 湖北孝感 | 1 | | 6 | 代鹏 | 5号楼 | 江苏盐城 | 85 | | 7 | 子栋 | 6号楼 | 湖北洪湖 | 95 | | 9 | 大爷 | 5号楼 | 湖北通城 | 82 | +----+--------+---------+--------------+-------+ 5 rows in set (0.00 sec)
mysql> select * from test_info where score between 60 and 80; #分数在60到80之间
mysql> select * from test_info where score between 60 and 80; +----+--------+---------+--------------+-------+ | id | name | dorm | addr | score | +----+--------+---------+--------------+-------+ | 1 | 科比 | 6号楼 | 湖北罗田 | 67 | | 2 | 毛线 | 6号楼 | 湖北孝感 | 78 | | 3 | 黄鱼 | 5号楼 | 湖北罗田 | 75 | +----+--------+---------+--------------+-------+ 3 rows in set (0.00 sec) #注意between包含两边
mysql> select * from test_info where addr in ("湖北罗田","湖北孝感"); #某个字段在某一个选择之内
mysql> select * from test_info where addr in ("湖北罗田","湖北孝感"); +----+--------+---------+--------------+-------+ | id | name | dorm | addr | score | +----+--------+---------+--------------+-------+ | 1 | 科比 | 6号楼 | 湖北罗田 | 67 | | 2 | 毛线 | 6号楼 | 湖北孝感 | 78 | | 3 | 黄鱼 | 5号楼 | 湖北罗田 | 75 | | 5 | 星爷 | 5号楼 | 湖北孝感 | 1 | +----+--------+---------+--------------+-------+ 4 rows in set (0.00 sec) mysql> select * from test_info where addr not in ("湖北罗田","湖北孝感"); +----+--------+---------+--------------+-------+ | id | name | dorm | addr | score | +----+--------+---------+--------------+-------+ | 4 | 子豪 | 6号楼 | 江苏扬州 | 45 | | 6 | 代鹏 | 5号楼 | 江苏盐城 | 85 | | 7 | 子栋 | 6号楼 | 湖北洪湖 | 95 | | 8 | 周攀 | 6号楼 | 湖北武穴 | 56 | | 9 | 大爷 | 5号楼 | 湖北通城 | 82 | | 10 | 小鸟 | 6号楼 | 湖北襄阳 | 38 | +----+--------+---------+--------------+-------+ 6 rows in set (0.00 sec)
模糊查询（like）
mysql> select name from test_info where addr like ‘__罗田‘; #查询罗田
mysql> select name from test_info where addr like ‘__罗田‘; +--------+ | name | +--------+ | 科比 | | 黄鱼 | +--------+ 2 rows in set (0.00 sec)
（2）排序（order by）
mysql> select * from test_info order by score; #按照成绩升序
mysql> select * from test_info order by score; +----+--------+---------+--------------+-------+ | id | name | dorm | addr | score | +----+--------+---------+--------------+-------+ | 5 | 星爷 | 5号楼 | 湖北孝感 | 1 | | 10 | 小鸟 | 6号楼 | 湖北襄阳 | 38 | | 4 | 子豪 | 6号楼 | 江苏扬州 | 45 | | 8 | 周攀 | 6号楼 | 湖北武穴 | 56 | | 1 | 科比 | 6号楼 | 湖北罗田 | 67 | | 3 | 黄鱼 | 5号楼 | 湖北罗田 | 75 | | 2 | 毛线 | 6号楼 | 湖北孝感 | 78 | | 9 | 大爷 | 5号楼 | 湖北通城 | 82 | | 6 | 代鹏 | 5号楼 | 江苏盐城 | 85 | | 7 | 子栋 | 6号楼 | 湖北洪湖 | 95 | +----+--------+---------+--------------+-------+ 10 rows in set (0.00 sec)
mysql> select * from test_info order by score desc; #降序
mysql> select * from test_info order by score desc; +----+--------+---------+--------------+-------+ | id | name | dorm | addr | score | +----+--------+---------+--------------+-------+ | 7 | 子栋 | 6号楼 | 湖北洪湖 | 95 | | 6 | 代鹏 | 5号楼 | 江苏盐城 | 85 | | 9 | 大爷 | 5号楼 | 湖北通城 | 82 | | 2 | 毛线 | 6号楼 | 湖北孝感 | 78 | | 3 | 黄鱼 | 5号楼 | 湖北罗田 | 75 | | 1 | 科比 | 6号楼 | 湖北罗田 | 67 | | 8 | 周攀 | 6号楼 | 湖北武穴 | 56 | | 4 | 子豪 | 6号楼 | 江苏扬州 | 45 | | 10 | 小鸟 | 6号楼 | 湖北襄阳 | 38 | | 5 | 星爷 | 5号楼 | 湖北孝感 | 1 | +----+--------+---------+--------------+-------+
mysql> select * from test_info order by score desc limit 3; #取成绩的前三名
mysql> select * from test_info order by score desc limit 3; +----+--------+---------+--------------+-------+ | id | name | dorm | addr | score | +----+--------+---------+--------------+-------+ | 7 | 子栋 | 6号楼 | 湖北洪湖 | 95 | | 6 | 代鹏 | 5号楼 | 江苏盐城 | 85 | | 9 | 大爷 | 5号楼 | 湖北通城 | 82 | +----+--------+---------+--------------+-------+
（3）分组（group by）
mysql> select * from test_info group by dorm; #按照宿舍分组
mysql> select * from test_info group by dorm; +----+--------+---------+--------------+-------+ | id | name | dorm | addr | score | +----+--------+---------+--------------+-------+ | 3 | 黄鱼 | 5号楼 | 湖北罗田 | 75 | | 1 | 科比 | 6号楼 | 湖北罗田 | 67 | +----+--------+---------+--------------+-------+ 2 rows in set (0.00 sec)
mysql> select *,group_concat(name) from test_info group by dorm; #查看组成员
mysql> select *,group_concat(name) from test_info group by dorm; +----+--------+---------+--------------+-------+-------------------------------------------+ | id | name | dorm | addr | score | group_concat(name) | +----+--------+---------+--------------+-------+-------------------------------------------+ | 6 | 代鹏 | 5号楼 | 江苏盐城 | 85 | 代鹏,大爷,黄鱼,星爷 | | 8 | 周攀 | 6号楼 | 湖北武穴 | 56 | 周攀,子栋,科比,子豪,毛线,小鸟 | +----+--------+---------+--------------+-------+-------------------------------------------+ 2 rows in set (0.00 sec)
（4）函数
max()：最大值
mysql> select max(score) from test_info; #查询最高分
mysql> select max(score) from test_info; +------------+ | max(score) | +------------+ | 95 | +------------+ 1 row in set (0.00 sec)
mysql> ) select * from test_info where score = (select max(score) from test_info); #最高分的学员信息
mysql> select * from test_info where score = (select max(score) from test_info); +----+--------+---------+--------------+-------+ | id | name | dorm | addr | score | +----+--------+---------+--------------+-------+ | 7 | 子栋 | 6号楼 | 湖北洪湖 | 95 | +----+--------+---------+--------------+-------+ 1 row in set (0.00 sec)
min()：最小值
mysql> select min(score) from test_info; #查询最低分
mysql> select min(score) from test_info; +------------+ | min(score) | +------------+ | 1 | +------------+ 1 row in set (0.00 sec)
sum()：求和
mysql> select sum(score) from test_info; #成绩总和
mysql> select sum(score) from test_info; +------------+ | sum(score) | +------------+ | 622 | +------------+ 1 row in set (0.00 sec)
avg()：平均值
mysql> select sum(score) from test_info; #求平均值
mysql> select sum(score) from test_info; +------------+ | sum(score) | +------------+ | 622 | +------------+ 1 row in set (0.00 sec)
count()：计数
mysql> select count(dorm) from test_info; #统计行数
mysql> select count(dorm) from test_info; +-------------+ | count(dorm) | +-------------+ | 10 | +-------------+ 1 row in set (0.00 sec)
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