MySQL常见命令管理
（1）语法：selectfromwhere #其中，select,from,where是不能随便改的，是关键字，支持大小写（2）不进入库查询
MariaDB [(none)]> select * from oldboy.test1 where name="oldboy";
+----+--------+------+
|> +----+--------+------+
|1 | oldboy | 40 |
+----+--------+------+
1 row in set (0.01 sec)
（3）只查询前2行
MariaDB > select * from test1 limit 2;
+----+---------+------+
|> +----+---------+------+
|1 | oldboy| 40 |
|2 | oldgirl | 60 |
+----+---------+------+
2 rows in set (0.00 sec)
（4）从第二条开始查，查找2个
MariaDB > select * from test1 limit 1,2;
+----+---------+------+
|> +----+---------+------+
|2 | oldgirl | 60 |
|3 | inca | 20 |
+----+---------+------+
2 rows in set (0.00 sec)
（5）按照条件查询
MariaDB [(none)]> select * from oldboy.test1 where name="oldboy";
+----+--------+------+
|> +----+--------+------+
|1 | oldboy | 40 |
+----+--------+------+
#提示：查找字符串类型的条件的值要带单引号，数字值不带引号。
（6）查询多个条件
MariaDB > select * from test1 where name='oldgirl' and> +----+---------+------+
|> +----+---------+------+
|2 | oldgirl | 60 |
+----+---------+------+
1 row in set (0.00 sec)
（7）范围查询
MariaDB > select * from test1 where> +----+------+------+
|> +----+------+------+
|3 | inca | 20 |
|4 | zuma | 30 |
|5 | kaka | 33 |
+----+------+------+
3 rows in set (0.00 sec)
（8）示例：
创建学生表
drop table student;
create table student(
Sno int(10) NOT NULL COMMENT '学号',
Sname varchar(16) NOT NULL COMMENT '姓名',
Ssex char(2) NOT NULL COMMENT '性别',
Sage tinyint(2)NOT NULL default '0' COMMENT '学生年龄',
Sdept varchar(16)default NULLCOMMENT '学生所在系别',
PRIMARY KEY(Sno) ,
key index_Sname (Sname)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=latin1;
插入内容
create table course(
Cno int(10) NOT NULL COMMENT '课程号',
Cname varchar(64) NOT NULL COMMENT '课程名',
Ccredit tinyint(2) NOT NULL COMMENT '学分',
PRIMARY KEY(Cno)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=latin1;
插入内容
CREATE TABLE `SC` (
SCid int(12) NOT NULL auto_increment COMMENT '主键',
`Cno` int(10) NOT NULL COMMENT '课程号',
`Sno` int(10) NOT NULL COMMENT '学号',
`Grade` tinyint(2) NOT NULL COMMENT '学生成绩',
PRIMARY KEY(`SCid`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
插入内容
INSERT INTO course values(1001,'Linux中高级运维',3);
INSERT INTO course values(1002,'Linux高级架构师',5);
INSERT INTO course values(1003,'MySQL高级Dba',4);
INSERT INTO course values(1004,'Python运维开发',4);
INSERT INTO course values(1005,'Java web开发',3);
插入内容
INSERT INTO SC(Sno,Cno,Grade)values(0001,1001,4);
INSERT INTO SC(Sno,Cno,Grade) values(0001,1002,3);
INSERT INTO SC(Sno,Cno,Grade)values(0001,1003,1);
INSERT INTO SC(Sno,Cno,Grade)values(0001,1004,6);
INSERT INTO SC(Sno,Cno,Grade)values(0002,1001,3);
INSERT INTO SC(Sno,Cno,Grade)values(0002,1002,2);
INSERT INTO SC(Sno,Cno,Grade)values(0002,1003,2);
INSERT INTO SC(Sno,Cno,Grade)values(0002,1004,8);
INSERT INTO SC(Sno,Cno,Grade)values(0003,1001,4);
INSERT INTO SC(Sno,Cno,Grade)values(0003,1002,4);
INSERT INTO SC(Sno,Cno,Grade)values(0003,1003,2);
INSERT INTO SC(Sno,Cno,Grade)values(0003,1004,8);
INSERT INTO SC(Sno,Cno,Grade)values(0004,1001,1);
INSERT INTO SC(Sno,Cno,Grade)values(0004,1002,1);
INSERT INTO SC(Sno,Cno,Grade)values(0004,1003,2);
INSERT INTO SC(Sno,Cno,Grade)values(0004,1004,3);
INSERT INTO SC(Sno,Cno,Grade)values(0005,1001,5);
INSERT INTO SC(Sno,Cno,Grade)values(0005,1002,3);
INSERT INTO SC(Sno,Cno,Grade)values(0005,1003,2);
INSERT INTO SC(Sno,Cno,Grade)values(0005,1004,9);
检查，查看表格式或者表内容
MariaDB > desc SC; or select * from SC;
+-------+------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+------------+------+-----+---------+----------------+
| SCid| int(12) | NO | PRI | NULL | auto_increment |
| Cno | int(10) | NO | | NULL | |
| Sno | int(10) | NO | | NULL | |
| Grade | tinyint(2) | NO | | NULL | |
+-------+------------+------+-----+---------+----------------+
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