MYSQL完全手册学习笔记（第四章）

MYSQL完全手册学习笔记


SQL基础

User 库名——使用某个库

Show 表名——显示表的各个字段

Select count (*) from callslog  ——显示一共有多少条记录


mysql> create database toys;——建立个数据库
Query OK, 1 row affected (0.02 sec)

mysql> use toys;
Database changed
mysql> show tables;
Empty set (0.01 sec)

mysql> create table user(id int(11) not null auto_increment,primary key(id));
建立个表

mysql> create table status(id int(11) not null,video_id tinyint(11) not null);
Query OK, 0 rows affected (0.08 sec)

mysql> alter table status add (hyht varchar(255));
Query OK, 0 rows affected (0.28 sec)
Records: 0  Duplicates: 0  Warnings: 0

增加字段

mysql> alter table status rename haha;
Query OK, 0 rows affected (0.03 sec)


Alter的用法
mysql> CREATE TABLE t1 (a INTEGER,b CHAR(10));
重命名表，从t1到t2:
mysql> ALTER TABLE t1 RENAME t2;
为了改变列a，从INTEGER改为TINYINT NOT NULL(名字一样)，并且改变列b，从CHAR(10)改为CHAR(20)，同时重命名它，从b改为c：
mysql> ALTER TABLE t2 MODIFY a TINYINT NOT NULL, CHANGE b c CHAR(20);
增加一个新TIMESTAMP列，名为d：
mysql> ALTER TABLE t2 ADD d TIMESTAMP;
在列d上增加一个索引，并且使列a为主键：
mysql> ALTER TABLE t2 ADD INDEX (d), ADD PRIMARY KEY (a);
删除列c：
mysql> ALTER TABLE t2 DROP COLUMN c;
增加一个新的AUTO_INCREMENT整数列，命名为c：
mysql> ALTER TABLE t2 ADD c INT UNSIGNED NOT NULL AUTO_INCREMENT,
           ADD INDEX (c);
注意，我们索引了c，因为AUTO_INCREMENT柱必须被索引，并且另外我们声明c为NOT NULL，因为索引了的列不能是NULL。 当你增加一个AUTO_INCREMENT列时，自动地用顺序数字填入列值。


mysql> insert into t2 (a,c)values(1,'hghg');
Query OK, 1 row affected (0.03 sec)
添加记录

mysql> alter table t2 drop column c;
Query OK, 0 rows affected (0.25 sec)
Records: 0  Duplicates: 0  Warnings: 0

删除列


mysql> alter table t2 add (c varchar(255));
Query OK, 0 rows affected (0.25 sec)
Records: 0  Duplicates: 0  Warnings: 0
增加列

注意：一个表中必须有主键才能在mysql插件中直接编辑，否则edit那项为灰色


mysql> delete from haha where video_id=2;
Query OK, 1 row affected (0.03 sec)
有条件的删除数据


mysql> update haha set hyht='tt'where hyht='1';
Query OK, 2 rows affected (0.02 sec)
Rows matched: 2  Changed: 2  Warnings: 0
更新数据


mysql> select * from haha;
+----+----------+------+
| id | video_id | hyht |
+----+----------+------+
|  1 |        3 | tt   |
|  2 |        3 | erer |
|  3 |        3 | tt   |
|  4 |        1 | tt   |
|  5 |        2 | tt   |
+----+----------+------+
5 rows in set (0.01 sec)

mysql> select hyht from haha
+------+
| hyht |
+------+
| tt   |
| erer |
| tt   |
| tt   |
| tt   |
+------+
5 rows in set (0.00 sec)

mysql> select distinct hyht
+------+
| hyht |
+------+
| tt   |
| erer |
+------+
2 rows in set (0.01 sec)

三个select 查询语句



mysql> select * from haha where video_id>2;
+----+----------+------+
| id | video_id | hyht |
+----+----------+------+
|  1 |        3 | tt   |
|  2 |        3 | erer |
|  3 |        3 | tt   |
+----+----------+------+
3 rows in set (0.00 sec)


mysql> select * from chengji;
+----+-------+------+---------+------------+
| id | name  | math | physics | literature |
+----+-------+------+---------+------------+
|  1 | john  |   60 |      37 |         45 |
|  2 | jim   |   96 |      89 |         92 |
|  3 | bill  |   65 |      12 |         57 |
|  4 | harry |   69 |      85 |         12 |
+----+-------+------+---------+------------+
4 rows in set (0.00 sec)
查询chengji表


mysql> select * from chengji where math>90;
+----+------+------+---------+------------+
| id | name | math | physics | literature |
+----+------+------+---------+------------+
|  2 | jim  |   96 |      89 |         92 |
+----+------+------+---------+------------+
1 row in set (0.00 sec)
查询math〉90 分的人


mysql> select name from chengji where math>85 and physics>85 and literature >85;

+------+
| name |
+------+
| jim  |
+------+
1 row in set (0.00 sec)
查询出来的优秀学生

mysql> select * from chengji where math<25 or physics <25 or literature <25;
+----+-------+------+---------+------------+
| id | name  | math | physics | literature |
+----+-------+------+---------+------------+
|  3 | bill  |   65 |      12 |         57 |
|  4 | harry |   69 |      85 |         12 |
+----+-------+------+---------+------------+
2 rows in set (0.00 sec)

其中有一门没有过25分的学生


mysql> select name,math+physics+literature from chengji;
+-------+-------------------------+
| name  | math+physics+literature |
+-------+-------------------------+
| john  |                     142 |
| jim   |                     277 |
| bill  |                     134 |
| harry |                     166 |
+-------+-------------------------+


得出三门成绩的总分数

mysql> select name,math+physics+literature as zf from chengji order by zf;
+-------+-----+
| name  | zf  |
+-------+-----+
| bill  | 134 |
| john  | 142 |
| harry | 166 |
| jim   | 277 |
+-------+-----+
4 rows in set (0.00 sec)

按照从低到高排列

mysql> select name,math+physics+literature as zf from chengji order by zf desc

+-------+-----+
| name  | zf  |
+-------+-----+
| jim   | 277 |
| harry | 166 |
| john  | 142 |
| bill  | 134 |
+-------+-----+
4 rows in set (0.00 sec)


按照从高到低的顺序排列


内建函数
Sum、avg、min、max、

mysql> select avg(math), avg(physics) from chengji;
+-----------+--------------+
| avg(math) | avg(physics) |
+-----------+--------------+
|   72.5000 |      55.7500 |
+-----------+--------------+
1 row in set (0.00 sec)


mysql> select min(math) from chengji;
+-----------+
| min(math) |
+-----------+
|        60 |
+-----------+
1 row in set (0.00 sec)

mysql> select max(math) from chegnji;
ERROR 1146 (42S02): Table 'toys.chegnji' doesn't exist
mysql> select max(math) from chengji;
+-----------+
| max(math) |
+-----------+
|        96 |
+-----------+
1 row in set (0.00 sec)




Limit后面跟的2个参数是从开始行的位置和要显示行的个数
mysql> select * from chengji order by math desc limit 0,4;
+----+-------+------+---------+------------+
| id | name  | math | physics | literature |
+----+-------+------+---------+------------+
|  2 | jim   |   96 |      89 |         92 |
|  4 | harry |   69 |      85 |         12 |
|  3 | bill  |   65 |      12 |         57 |
|  1 | john  |   60 |      37 |         45 |
+----+-------+------+---------+------------+
4 rows in set (0.00 sec)

mysql> select * from chengji order by math desc limit 2,4;
+----+------+------+---------+------------+
| id | name | math | physics | literature |
+----+------+------+---------+------------+
|  3 | bill |   65 |      12 |         57 |
|  1 | john |   60 |      37 |         45 |
+----+------+------+---------+------------+
2 rows in set (0.00 sec)


通配符模糊查询
mysql> select *  from chengji where name like '%j%';
+----+------+------+---------+------------+
| id | name | math | physics | literature |
+----+------+------+---------+------------+
|  1 | john |   60 |      37 |         45 |
|  2 | jim  |   96 |      89 |         92 |
+----+------+------+---------+------------+
2 rows in set (0.00 sec)

mysql> select math  from chengji where name like '%j%';
+------+
| math |
+------+
|   60 |
|   96 |
+------+
2 rows in set (0.02 sec)



mysql> select name,math from chengji where math like '%9%';
+-------+------+
| name  | math |
+-------+------+
| jim   |   96 |
| harry |   69 |
+-------+------+
2 rows in set (0.00 sec)


mysql> select * from haha,chengji;
查询多个表里面所有字段，也可以查询出来需要的字段

mysql> select m.hyht,v.math from haha m,chengji v;

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