MySQL学习总结之路（第二章：表）-编程学习网

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MySQL学习总结之路（第二章：表）

1、创建表

1.1、创建表基本语法：

CREATE TABLE tablename (column_name_1 column_type_1 constraints，
column_name_2 column_type_2 constraints ， ……）

column_name 是列的名字 column_type 是列的数据类型 contraints 是这个列的约束条件

1.1.1、创建一张简单的表

mysql> create table orders (ordername varchar(10),createtime date,ordermoney decimal(10,2),ordernumber int(2));
Query OK, 0 rows affected (0.23 sec)

1.1.2、查看创建表定义

1.1.2.1、结构化定义

mysql> desc orders;
+-------------+---------------+------+-----+---------+-------+
| Field       | Type          | Null | Key | Default | Extra |
+-------------+---------------+------+-----+---------+-------+
| ordername   | varchar(10)   | YES  |     | NULL    |       |
| createtime  | date          | YES  |     | NULL    |       |
| ordermoney  | decimal(10,2) | YES  |     | NULL    |       |
| ordernumber | int(2)        | YES  |     | NULL    |       |
+-------------+---------------+------+-----+---------+-------+
4 rows in set (0.00 sec)

1.1.2.2、表详细定义

查看详细的表定义

mysql> show create table orders G;
*************************** 1. row ***************************
       Table: orders
Create Table: CREATE TABLE `orders` (
  `ordername` varchar(10) DEFAULT NULL,
  `createtime` date DEFAULT NULL,
  `ordermoney` decimal(10,2) DEFAULT NULL,
  `ordernumber` int(2) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1
1 row in set (0.00 sec)

ERROR:
No query specified

由此可以看到表的 ENGINE（存储引擎）是InnoDB

　　　　　　　　 CHARSET（字符集）是Latin1

“G”选项的含义是使得记录能够按照字段竖着排列，对于内容比较长的记录更易于显示。

2、删除表

命令：

DROP TABLE tablename

删除orders：

mysql> drop table orders
    -> ;
Query OK, 0 rows affected (0.14 sec)

3、修改表

3.1、修改表类型命令：

ALTER TABLE tablename MODIFY [COLUMN] column_definition [FIRST | AFTER col_name]

例：修改表 orders 的 name 字段定义，将 varchar(10)改为 varchar(20)：

mysql> alter table orders modify ordername varchar(20);
Query OK, 0 rows affected (0.11 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc orders;
+-------------+---------------+------+-----+---------+-------+
| Field       | Type          | Null | Key | Default | Extra |
+-------------+---------------+------+-----+---------+-------+
| ordername   | varchar(20)   | YES  |     | NULL    |       |
| createtime  | date          | YES  |     | NULL    |       |
| ordermoney  | decimal(10,2) | YES  |     | NULL    |       |
| ordernumber | int(2)        | YES  |     | NULL    |       |
+-------------+---------------+------+-----+---------+-------+
4 rows in set (0.00 sec)

3.2、字段改名命令：

ALTER TABLE tablename CHANGE [COLUMN] old_col_name column_definition
[FIRST|AFTER col_name]

例：表 orders 上将ordernumber修改为ordernumbers

mysql> alter table orders change column ordernumber ordernumbers int(4);
Query OK, 0 rows affected (0.06 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc orders;
+--------------+---------------+------+-----+---------+-------+
| Field        | Type          | Null | Key | Default | Extra |
+--------------+---------------+------+-----+---------+-------+
| ordername    | varchar(20)   | YES  |     | NULL    |       |
| createtime   | date          | YES  |     | NULL    |       |
| ordermoney   | decimal(10,2) | YES  |     | NULL    |       |
| ordernumbers | int(4)        | YES  |     | NULL    |       |
+--------------+---------------+------+-----+---------+-------+
4 rows in set (0.00 sec)

特别说明：change 和 modify 都可以修改表的定义，不同的是 change 后面需要写两次列名，不方便。但是 change 的优点是可以修改列名称，modify 则不能。

3.3、增加表字段命令：

ALTER TABLE tablename ADD [COLUMN] column_definition [FIRST | AFTER col_name]

例：表 orders 上新增加字段 username，类型为 varchar(3)：

mysql> alter table orders add column username varchar(30);
Query OK, 0 rows affected (0.39 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc orders;
+-------------+---------------+------+-----+---------+-------+
| Field       | Type          | Null | Key | Default | Extra |
+-------------+---------------+------+-----+---------+-------+
| ordername   | varchar(20)   | YES  |     | NULL    |       |
| createtime  | date          | YES  |     | NULL    |       |
| ordermoney  | decimal(10,2) | YES  |     | NULL    |       |
| ordernumber | int(2)        | YES  |     | NULL    |       |
| username    | varchar(30)   | YES  |     | NULL    |       |
+-------------+---------------+------+-----+---------+-------+
5 rows in set (0.00 sec)

3.4、删除表列字段命令

ALTER TABLE tablename DROP [COLUMN] col_name

例：表 orders 上删除字段 username：

mysql> alter table orders drop column username;
Query OK, 0 rows affected (0.53 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc orders;
+-------------+---------------+------+-----+---------+-------+
| Field       | Type          | Null | Key | Default | Extra |
+-------------+---------------+------+-----+---------+-------+
| ordername   | varchar(20)   | YES  |     | NULL    |       |
| createtime  | date          | YES  |     | NULL    |       |
| ordermoney  | decimal(10,2) | YES  |     | NULL    |       |
| ordernumber | int(2)        | YES  |     | NULL    |       |
+-------------+---------------+------+-----+---------+-------+
4 rows in set (0.00 sec)

3.5、表改名命令

ALTER TABLE tablename RENAME [TO] new_tablename

例：表 orders 名字改为goodsorders

mysql> alter table orders rename goodsorders;
Query OK, 0 rows affected (0.16 sec)

mysql> desc orders;
ERROR 1146 (42S02): Table "ordermanage.orders" doesn"t exist
mysql> desc goodsorders;
+--------------+---------------+------+-----+---------+-------+
| Field        | Type          | Null | Key | Default | Extra |
+--------------+---------------+------+-----+---------+-------+
| ordername    | varchar(20)   | YES  |     | NULL    |       |
| createtime   | date          | YES  |     | NULL    |       |
| ordermoney   | decimal(10,2) | YES  |     | NULL    |       |
| ordernumbers | int(4)        | YES  |     | NULL    |       |
+--------------+---------------+------+-----+---------+-------+
4 rows in set (0.00 sec)

4、DML 语句

插入（insert）、查询（select）、更新（update）、删除（delete）

4.1、插入记录命令

INSERT INTO tablename (field1,field2,……fieldn) VALUES(value1,value2,……valuesn);

例：表 goodsorders 中插入一条记录，ordername 为zhang，createtime为2021-05-12，ordermoney为100.00,ordernumbers为：1

mysql> insert into goodsorders (ordername,createtime,ordermoney,ordernumbers) values("zhang","2021-05-12",100.00,1);
Query OK, 1 row affected (0.03 sec)

也可以省略(field1,field2,……fieldn)这一部分

mysql> insert into goodsorders  values("zhang1","2021-05-12",1001.00,11);
Query OK, 1 row affected (0.05 sec)

4.2、查看插入数据命令

4.2.1、查询全部

SELECT * FROM tablename [WHERE CONDITION]

例：查看goodsorders中所有插入数据

mysql> select * from goodsorders;
+-----------+------------+------------+--------------+
| ordername | createtime | ordermoney | ordernumbers |
+-----------+------------+------------+--------------+
| zhang     | 2021-05-12 |     100.00 |            1 |
| zhang1    | 2021-05-12 |    1001.00 |           11 |
+-----------+------------+------------+--------------+
2 rows in set (0.00 sec)

其中“*”表示要将所有的记录都选出来

4.2.2、查询不重复记录命令关键字

distinct

例：查询非goodsorders中非重复创建时间（createtime）的数据

mysql> select  * from goodsorders;
+-----------+------------+------------+--------------+
| ordername | createtime | ordermoney | ordernumbers |
+-----------+------------+------------+--------------+
| zhang     | 2021-03-11 |      50.00 |            1 |
| li        | 2020-05-12 |      70.00 |           15 |
| li        | 2020-03-12 |      70.00 |           15 |
| li        | 2020-03-11 |      70.00 |           15 |
| li        | 2021-03-11 |      70.00 |           15 |
+-----------+------------+------------+--------------+
5 rows in set (0.00 sec)

mysql> select distinct createtime from goodsorders;
+------------+
| createtime |
+------------+
| 2021-03-11 |
| 2020-05-12 |
| 2020-03-12 |
| 2020-03-11 |
+------------+
4 rows in set (0.00 sec)

由此可以看到，将重复的一条时间数据2021-03-11去掉了

4.2.3、多条件查询关键字

where 后面的条件是一个字段的‘=’比较，还可以使用>、<、>=、<=、!=等比较运算符；
多个条件之间还可以使用 or、and 等逻辑运算符进行多条件联合查询，

例：查询非goodsorders中 ordername="li"并且createtime为2020-03-11

mysql> select * from goodsorders where ordername="li"and createtime ="2020-03-11";
+-----------+------------+------------+--------------+
| ordername | createtime | ordermoney | ordernumbers |
+-----------+------------+------------+--------------+
| li        | 2020-03-11 |      70.00 |           15 |
+-----------+------------+------------+--------------+
1 row in set (0.00 sec)

4.2.4、排序查询命名

SELECT * FROM tablename [WHERE CONDITION] [ORDER BY field1 [DESC|ASC] ， field2 
[DESC|ASC]，……fieldn [DESC|ASC]]

例：把 goodsorders表中的记录按照创建时间高低进行排序显示

mysql> select * from goodsorders order by createtime;
+-----------+------------+------------+--------------+
| ordername | createtime | ordermoney | ordernumbers |
+-----------+------------+------------+--------------+
| li        | 2020-03-11 |      70.00 |           15 |
| li        | 2020-03-12 |      70.00 |           15 |
| li        | 2020-05-12 |      70.00 |           15 |
| zhang     | 2021-03-11 |      50.00 |            1 |
| li        | 2021-03-11 |      70.00 |           15 |
+-----------+------------+------------+--------------+
5 rows in set (0.01 sec)

4.2.5、显示一部分，而不是全部，指令

SELECT ……[LIMIT offset_start,row_count]

offset_start 表示记录的起始偏移量 row_count 表示显示的行数例如1：显示 goodsorders表中按照 createtiem 排序后的前 3 条记录：

mysql> select * from goodsorders order by createtime limit 3;
+-----------+------------+------------+--------------+
| ordername | createtime | ordermoney | ordernumbers |
+-----------+------------+------------+--------------+
| li        | 2020-03-11 |      70.00 |           15 |
| li        | 2020-03-12 |      70.00 |           15 |
| li        | 2020-05-12 |      70.00 |           15 |
+-----------+------------+------------+--------------+
3 rows in set (0.00 sec)

例如2：如果要显示 goodsorders表中按照 createtiem 排序后从第二条记录开始，显示3条数据：

mysql> select * from goodsorders order by createtime limit 2,3;
+-----------+------------+------------+--------------+
| ordername | createtime | ordermoney | ordernumbers |
+-----------+------------+------------+--------------+
| li        | 2020-05-12 |      70.00 |           15 |
| zhang     | 2021-03-11 |      50.00 |            1 |
| li        | 2021-03-11 |      70.00 |           15 |
+-----------+------------+------------+--------------+
3 rows in set (0.00 sec)

4.2.6、统计数据，聚合指令

SELECT [field1,field2,……fieldn] fun_name 
FROM tablename
[WHERE where_contition]
[GROUP BY field1,field2,……fieldn
[WITH ROLLUP]]
[HAVING where_contition]

参数说明：

fun_name 表示要做的聚合操作，也就是聚合函数，常用的有 sum（求和）、count(*)（记录数）、max（最大值）、min（最小值）

GROUP BY 关键字表示要进行分类聚合的字段，比如要按照部门分类统计员工数量，部门就应该写在 group by 后面。

3、WITH ROLLUP 是可选语法，表明是否对分类聚合后的结果进行再汇总。 4、HAVING 关键字表示对分类后的结果再进行条件的过滤。注意：having 和 where 的区别在于 having 是对聚合后的结果进行条件的过滤，而 where 是在聚合前就对记录进行过滤，如果逻辑允许，我们尽可能用 where 先过滤记录，这样因为结果集减小，将对聚合的效率大大提高，最后再根据逻辑看是否用 having 进行再过滤。例1：查询统计goodsorders表中，记录总数

mysql> select count(1) from goodsorders;
+----------+
| count(1) |
+----------+
|        5 |
+----------+
1 row in set (0.00 sec)

例2：在此基础上，按照创建日期（createtime）进行分组统计

mysql> select createtime,count(1) from goodsorders group by createtime;
+------------+----------+
| createtime | count(1) |
+------------+----------+
| 2020-03-11 |        1 |
| 2020-03-12 |        1 |
| 2020-05-12 |        1 |
| 2021-03-11 |        2 |
+------------+----------+
4 rows in set (0.00 sec)

例3：在此基础上，既要按照创建日期（cretetime）进行分组统计，又要计算总数

mysql> select createtime,count(1) from goodsorders group by createtime with rollup;
+------------+----------+
| createtime | count(1) |
+------------+----------+
| 2020-03-11 |        1 |
| 2020-03-12 |        1 |
| 2020-05-12 |        1 |
| 2021-03-11 |        2 |
| NULL       |        5 |
+------------+----------+
5 rows in set (0.02 sec)

最有一行，null所展示的数字，就是总数

例4：按照创建日期（createtime）进行分组统计，并且数量大于1

mysql> select createtime,count(1) from goodsorders group by createtime having count(1)>1;
+------------+----------+
| createtime | count(1) |
+------------+----------+
| 2021-03-11 |        2 |
+------------+----------+
1 row in set (0.00 sec)

例5：查询goodsorders表中，订单金额（ordermoney）的总额、最低额、最高额

mysql> select * from goodsorders;
+-----------+------------+------------+--------------+
| ordername | createtime | ordermoney | ordernumbers |
+-----------+------------+------------+--------------+
| zhang     | 2021-03-11 |      50.00 |            1 |
| li        | 2020-05-12 |      70.00 |           15 |
| li        | 2020-03-12 |      70.00 |           15 |
| li        | 2020-03-11 |      70.00 |           15 |
| li        | 2021-03-11 |      70.00 |           15 |
+-----------+------------+------------+--------------+
5 rows in set (0.00 sec)

mysql> select sum(ordermoney),max(ordermoney),min(ordermoney) from goodsorders;
+-----------------+-----------------+-----------------+
| sum(ordermoney) | max(ordermoney) | min(ordermoney) |
+-----------------+-----------------+-----------------+
|          330.00 |           70.00 |           50.00 |
+-----------------+-----------------+-----------------+
1 row in set (0.02 sec)

4.2.7、表连接

左连接：包含所有的左边表中的记录甚至是右边表中没有和它匹配的记录；关键指令：left join

右连接：包含所有的右边表中的记录甚至是左边表中没有和它匹配的记录；关联指令：right join

例1：现在我们又创建一张用户表（member）,使用goodorders进行左连接，查询关联的用户表信息

mysql> select * from member;
+------+------------+
| id   | membername |
+------+------------+
| 15   | zhang      |
| 1    | li         |
| 13   | liss       |
+------+------------+
3 rows in set (0.00 sec)

mysql> select * from goodsorders;
+-----------+------------+------------+--------------+----------+
| ordername | createtime | ordermoney | ordernumbers | memberid |
+-----------+------------+------------+--------------+----------+
| zhang     | 2021-03-11 |      50.00 |            1 | 15       |
| li        | 2020-05-12 |      70.00 |           15 | 1        |
| li        | 2020-03-12 |      70.00 |           15 | 1        |
| li        | 2020-03-11 |      70.00 |           15 | 3        |
| li        | 2021-03-11 |      70.00 |           15 | 1        |
+-----------+------------+------------+--------------+----------+
5 rows in set (0.00 sec)

mysql> select * from goodsorders left join member on goodsorders.memberid = member.id;
+-----------+------------+------------+--------------+----------+------+------------+
| ordername | createtime | ordermoney | ordernumbers | memberid | id   | membername |
+-----------+------------+------------+--------------+----------+------+------------+
| zhang     | 2021-03-11 |      50.00 |            1 | 15       | 15   | zhang      |
| li        | 2020-05-12 |      70.00 |           15 | 1        | 1    | li         |
| li        | 2020-03-12 |      70.00 |           15 | 1        | 1    | li         |
| li        | 2021-03-11 |      70.00 |           15 | 1        | 1    | li         |
| li        | 2020-03-11 |      70.00 |           15 | 3        | NULL | NULL       |
+-----------+------------+------------+--------------+----------+------+------------+
5 rows in set (0.00 sec)

例2：member和goodsorders中数据不变，我们再来看一下右连接的查询，以及结果：

mysql> select * from goodsorders right join member on goodsorders.memberid = member.id;
+-----------+------------+------------+--------------+----------+------+------------+
| ordername | createtime | ordermoney | ordernumbers | memberid | id   | membername |
+-----------+------------+------------+--------------+----------+------+------------+
| zhang     | 2021-03-11 |      50.00 |            1 | 15       | 15   | zhang      |
| li        | 2020-05-12 |      70.00 |           15 | 1        | 1    | li         |
| li        | 2020-03-12 |      70.00 |           15 | 1        | 1    | li         |
| li        | 2021-03-11 |      70.00 |           15 | 1        | 1    | li         |
| NULL      | NULL       |       NULL |         NULL | NULL     | 13   | liss       |
+-----------+------------+------------+--------------+----------+------+------------+
5 rows in set (0.00 sec)

这里发生了翻转，变为左侧goodsorders 表中的一条数据为空了

4.2.8、子查询，相关关键字

主要包括 in、not in、=、!=、exists、not exists 等

例：从goodsorders表中查询所有用户在memeber表中的记录

mysql> select * from member;
+------+------------+
| id   | membername |
+------+------------+
| 15   | zhang      |
| 1    | li         |
| 13   | liss       |
+------+------------+
3 rows in set (0.00 sec)

mysql> select * from goodsorders;
+-----------+------------+------------+--------------+----------+
| ordername | createtime | ordermoney | ordernumbers | memberid |
+-----------+------------+------------+--------------+----------+
| zhang     | 2021-03-11 |      50.00 |            1 | 15       |
| li        | 2020-05-12 |      70.00 |           15 | 1        |
| li        | 2020-03-12 |      70.00 |           15 | 1        |
| li        | 2020-03-11 |      70.00 |           15 | 3        |
| li        | 2021-03-11 |      70.00 |           15 | 1        |
+-----------+------------+------------+--------------+----------+
5 rows in set (0.00 sec)

mysql> select * from goodsorders where memberid in(select id from member);
+-----------+------------+------------+--------------+----------+
| ordername | createtime | ordermoney | ordernumbers | memberid |
+-----------+------------+------------+--------------+----------+
| zhang     | 2021-03-11 |      50.00 |            1 | 15       |
| li        | 2020-05-12 |      70.00 |           15 | 1        |
| li        | 2020-03-12 |      70.00 |           15 | 1        |
| li        | 2021-03-11 |      70.00 |           15 | 1        |
+-----------+------------+------------+--------------+----------+
4 rows in set (0.05 sec)

4.2.9、记录联合，指令

SELECT * FROM t1
UNION|UNION ALL
SELECT * FROM t2
……
UNION|UNION ALL
SELECT * FROM tn;

UNION 和 UNION ALL 的主要区别：　　UNION ALL 是把结果集直接合并在一起，　　 UNION 是将UNION ALL 后的结果进行一次 DISTINCT，去除重复记录后的结果。

例1：将member表和goodsorders表中的用户编号id（memberid）的集合显示出来

mysql> select memberid from goodsorders union all select id from member;
+----------+
| memberid |
+----------+
| 15       |
| 1        |
| 1        |
| 3        |
| 1        |
| 15       |
| 1        |
| 13       |
+----------+
8 rows in set (0.00 sec)

例2：如果希望将上面的结果去掉重复记录后显示

mysql> select memberid from goodsorders union select id from member;
+----------+
| memberid |
+----------+
| 15       |
| 1        |
| 3        |
| 13       |
+----------+
4 rows in set (0.00 sec)

4.3、更新记录命令

UPDATE tablename SET field1=value1，field2.=value2，……fieldn=valuen [WHERE CONDITION]

例：将表 goodsorders 中ordername为zhang的订单金额（ordermoney）改为50

mysql> update goodsorders set ordermoney=50.00 where ordername="zhang";
Query OK, 1 row affected (0.09 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from goodsorders;
+-----------+------------+------------+--------------+
| ordername | createtime | ordermoney | ordernumbers |
+-----------+------------+------------+--------------+
| zhang     | 2021-05-12 |      50.00 |            1 |
| zhang1    | 2021-05-12 |    1001.00 |           11 |
+-----------+------------+------------+--------------+
2 rows in set (0.00 sec)

4.4、删除记录命名

DELETE FROM tablename [WHERE CONDITION]

例：将表 goodsorders 中ordername为zhang1的记录全部删除

mysql> delete from goodsorders where ordername = "zhang1";
Query OK, 1 row affected (0.06 sec)

mysql> select * from goodsorders;
+-----------+------------+------------+--------------+
| ordername | createtime | ordermoney | ordernumbers |
+-----------+------------+------------+--------------+
| zhang     | 2021-05-12 |      50.00 |            1 |
+-----------+------------+------------+--------------+
1 row in set (0.02 sec)

5、DCL 语句

DCL语句主要是为了管理数据库系统中的操作对象权限

5.1创建数据库用户

例：创建一个数据库用户 user1,初始密码为123，具有对 ordermanage 数据库中所有表的 SELECT/INSERT 权限：

mysql> grant select,insert on ordermanage.* to "user1"@"localhost" identified by "123";
Query OK, 0 rows affected, 1 warning (0.06 sec)

mysql> exit
Bye


C:Program FilesMySQLMySQL Server 5.7in>mysql -uuser1 -p123
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 82
Server version: 5.7.17-log MySQL Community Server (GPL)

Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type "help;" or "h" for help. Type "c" to clear the current input statement.

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| ordermanage        |
+--------------------+
2 rows in set (0.00 sec)

在此基础上，将此用户（user1）的insert权限进行收回

mysql> revoke insert on ordermanage.* from "user1"@"localhost";
Query OK, 0 rows affected (0.02 sec)

mysql> exit
Bye

C:Program FilesMySQLMySQL Server 5.7in>mysql -uuser1 -p123
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 84
Server version: 5.7.17-log MySQL Community Server (GPL)

Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type "help;" or "h" for help. Type "c" to clear the current input statement.

mysql> use ordermanage;
Database changed

mysql> insert into member values("11","ss");
ERROR 1142 (42000): INSERT command denied to user "user1"@"localhost" for table "member"
mysql>

由此可以看出插入权限不足，插入失败

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MySQL学习总结之路（第二章：表）

目录

1、创建表

1.1、创建表基本语法：

1.1.1、创建一张简单的表

1.1.2、查看创建表定义

1.1.2.1、结构化定义

1.1.2.2、表详细定义

2、删除表

3、修改表

3.1、修改表类型命令：

3.2、字段改名命令：

3.3、增加表字段命令：

3.4、删除表列字段命令

3.5、表改名命令

4、DML 语句

4.1、插入记录 命令

4.2、查看插入数据命令

4.2.1、查询全部

4.2.2、查询不重复记录命令关键字

4.2.3、多条件查询关键字

4.2.4、排序查询命名

4.2.5、显示一部分，而不是全部，指令

4.2.6、统计数据，聚合指令

4.2.7、表连接

4.2.8、子查询，相关关键字

4.2.9、记录联合，指令

4.3、更新记录命令

4.4、删除记录命名

5、DCL 语句

5.1创建数据库用户

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4.1、插入记录命令