一、导入测试数据
[[email protected] ~]# wget https://launchpadlibrarian.net/24493586/employees_db-full-1.0.6.tar.bz2
mysql> source /root/employees_db/employees.sql ;
查看：
mysql> use employees;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> show tables;
+---------------------+
| Tables_in_employees |
+---------------------+
| departments |
| dept_emp |
| dept_manager |
| employees |
| salaries |
| titles |
+---------------------+
6 rows in set (0.00 sec)
二、数据表
表是关系型数据库的核心，表是记录的集合（集合中的数据是无序的）
二维表模型易于人类理解，mysql默认存储引擎都是基于行存储
每行记录都是基于列进行组织的
语法：
官网：https://dev.mysql.com/doc/refman/5.7/en/create-table.html
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
(create_definition,...)
[table_options]
[partition_options]
create_definition：
col_name column_definition
column_definition:
data_type [NOT NULL | NULL] [DEFAULT default_value]
[AUTO_INCREMENT] [UNIQUE [KEY]] [[PRIMARY] KEY]
[COMMENT ‘string‘]
[COLUMN_FORMAT {FIXED|DYNAMIC|DEFAULT}]
[STORAGE {DISK|MEMORY|DEFAULT}]
[reference_definition]
| data_type [GENERATED ALWAYS] AS (expression)
[VIRTUAL | STORED] [NOT NULL | NULL]
[UNIQUE [KEY]] [[PRIMARY] KEY]
[COMMENT ‘string‘]
知识点1：创建临时表（temporary）
To create a temporary table, you must have the CREATE TEMPORARY TABLES privilege
mysql> create table a ( id int);
Query OK, 0 rows affected (0.20 sec)
mysql> insert into a select 5;
Query OK, 1 row affected (0.02 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> create temporary table a ( id int);
Query OK, 0 rows affected (0.00 sec)
mysql> show tables;
+------------------+
| Tables_in_testDB |
+------------------+
| a |
+------------------+
1 row in set (0.00 sec)
mysql> select * from a;
Empty set (0.00 sec)
mysql> insert into a select 6;
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> select * from a;
+------+
| id |
+------+
| 6 |
+------+
1 row in set (0.00 sec)
（综上，临时表的表明可以和实际存在的表名同名，但是建议不这样操作）
mysql> system ls /tmp -lh
-rw-r-----. 1 mysql mysql 8.4K Nov 28 16:38 #sql5ad7_f_0.frm
-rw-r-----. 1 mysql mysql 8.4K Nov 28 16:58 #sql5ad7_f_1.frm
数据存放到ibtmp1临时表空间
[[email protected] mysql_data1]# ll ibtmp1
-rw-r-----. 1 mysql mysql 12582912 Nov 28 17:05 ibtmp1
案例2：
mysql> create table orders ( o_orderkey int(11) not null,o_custkey int(11) default null,o_orderstatus char(1) default null,o_totalprice double default null,o_orderDATE date default null, o_clerk char(15) default null, o_orderpriority char(15) default null, o_comment varchar(79) default null,primary key (o_orderkey),key `i_o_custkey`(`o_custkey`));
Query OK, 0 rows affected (0.23 sec)
mysql> show create table orders\G
*************************** 1. row ***************************
Table: orders
Create Table: CREATE TABLE `orders` (
`o_orderkey` int(11) NOT NULL,
`o_custkey` int(11) DEFAULT NULL,
`o_orderstatus` char(1) DEFAULT NULL,
`o_totalprice` double DEFAULT NULL,
`o_orderDATE` date DEFAULT NULL,
`o_clerk` char(15) DEFAULT NULL,
`o_orderpriority` char(15) DEFAULT NULL,
`o_comment` varchar(79) DEFAULT NULL,
PRIMARY KEY (`o_orderkey`),
KEY `i_o_custkey` (`o_custkey`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)
mysql> show table status like ‘orders‘\G 查看表的状态
*************************** 1. row ***************************
Name: orders
Engine: InnoDB
Version: 10
Row_format: Dynamic
Rows: 0
Avg_row_length: 0
Data_length: 16384
Max_data_length: 0
Index_length: 16384
Data_free: 0
Auto_increment: NULL
Create_time: 2017-11-28 17:24:22
Update_time: NULL
Check_time: NULL
Collation: utf8_general_ci
Checksum: NULL
Create_options:
Comment:
1 row in set (0.00 sec)
二、外键约束
[CONSTRAINT [symbol]] FOREIGN KEY [index_name] (index_col_name,...) reference_definition | CHECK (expr)
reference_definition:
REFERENCES tbl_name (index_col_name,...)
[MATCH FULL | MATCH PARTIAL | MATCH SIMPLE]
[ON DELETE reference_option]
[ON UPDATE reference_option]
reference_option:
RESTRICT | CASCADE | SET NULL | NO ACTION | SET DEFAULT
案例1：
mysql> create table parent ( id int(11) not null,primary key(id))engine=innodb default charset=latin1;
Query OK, 0 rows affected (0.12 sec)
mysql> create table child( id int(11) default null, parent_id int(11) default null,key `par_id`(`parent_id`),constraint `child_ibfk_1` foreign key (`parent_id`) references parent (id) on delete cascade on update cascade);
Query OK, 0 rows affected (0.13 sec)
mysql> insert into parent values(1);
Query OK, 1 row affected (0.02 sec)
mysql> insert into child values (1,1);
Query OK, 1 row affected (0.05 sec)
mysql> update parent set id=2 where id=1;
Query OK, 1 row affected (0.03 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from child;
+------+-----------+
| id | parent_id |
+------+-----------+
| 1 | 2 |
+------+-----------+
1 row in set (0.00 sec)
（级别更新，on delete cascade on update cascade 只要父表发生变化，所引用的子表也会发生更新）