MySQL中的CREATE TABLE LIKE和CREATE TABLE SELECT

CREATE TABLE LIKE
CREATE TABLE SELECT

CREATE TABLE LIKE

CREATE TABLE ... LIKE可以用来复制表结构，源表上的索引和约束也会复制。
CREATE TABLE ... LIKE不能复制表数据。
CREATE TABLE ... LIKE只能复制基表，不能复制视图。
CREATE TABLE ... LIKE可以复制CHECK约束，但是复制后的约束名称是自动生成的。
CREATE TABLE ... LIKE不能复制外键约束，也不会保留DATA DIRECTORY和INDEX DIRECTORY表创建参数。
CREATE TABLE ... LIKE不会复制表的临时属性。要复制临时表请使用CREATE TEMPORARY TABLE LIKE。
当源表被LOCK TABLES锁定时，CREATE TABLE LIKE语句无法成功执行。

用法示例：

CREATE TABLE t1 LIKE t2;
CREATE TEMPORARY TABLE t1 LIKE t2;

CREATE TABLE SELECT

CREATE TABLE ... SELECT可以用来复制表结构，但不会复制索引（主键也不会）。
CREATE TABLE ... SELECT可以复制表数据（可以通过WHERE过滤）。
CREATE TABLE ... SELECT可以复制基表，也可以复制视图。
CREATE TABLE ... SELECT不能复制外键约束。
CREATE TABLE ... SELECT支持在建表时定义字段，从源表复制过来的不同名字段会作为新增字段，同名的字段则会被覆盖。
CREATE TABLE ... SELECT支持在建表时为字段定义约束和索引。

用法示例：

CREATE TABLE t1 SELECT * FROM t2 where 1=2;             --仅复制表结构
CREATE TABLE t1 SELECT * FROM t2;                       --复制全量数据
CREATE TABLE t1 SELECT name,age FROM t2 where age>30;   --复制部分数据--复制另外两张表关联查询的结果集
CREATE TABLE t1SELECT artist.name, COUNT(work.artist_id) AS number_of_worksFROM artist LEFT JOIN work ON artist.id = work.artist_idGROUP BY artist.id;--复制的列作为新增字段
CREATE TABLE t1 (a int) SELECT name,age FROM t2;  --复制的不同列作为新增字段，同名的列被覆盖      
CREATE TABLE t1 (a int, name varchar(30)) SELECT name,age FROM t2; --为复制过来的字段定义索引和约束
CREATE TABLE t1 (name varchar(30) not null) SELECT name,age FROM t2; 
CREATE TABLE t1 (unique(employee_id)) SELECT employee_id,name FROM t3;

实验：

SQL> create table t2 (name varchar(30), age int not null);
SQL> create table t3 (employ_id int, name varchar(30), age int);
SQL> insert into t2 values ('Joe',35),('Rachel',31),('Monica',33);
SQL> insert into t3 values (11,'MJoe',35),(12,'MRachel',31),(13,'MMonica',33);
SQL> commit;SQL> select * from t2;
+--------+-----+
| name   | age |
+--------+-----+
| Joe    |  35 |
| Rachel |  31 |
| Monica |  33 |
+--------+-----+
3 rows in set (0.00 sec)SQL> select * from t3;
+-----------+---------+------+
| employ_id | name    | age  |
+-----------+---------+------+
|        11 | MJoe    |   35 |
|        12 | MRachel |   31 |
|        13 | MMonica |   33 |
+-----------+---------+------+
3 rows in set (0.00 sec)--仅复制表结构
SQL> CREATE TABLE t1 SELECT * FROM t2 where 1=2; 
Query OK, 0 rows affected (0.11 sec)
Records: 0  Duplicates: 0  Warnings: 0SQL> select * from t1;
Empty set (0.00 sec)SQL> desc t1;
+-----------+-----------------+------+-----+---------+--------------------------+
| Field     | Type            | Null | Key | Default | Extra                    |
+-----------+-----------------+------+-----+---------+--------------------------+
| my_row_id | bigint unsigned | NO   | PRI | NULL    | auto_increment INVISIBLE |
| name      | varchar(30)     | YES  |     | NULL    |                          |
| age       | int             | NO   |     | NULL    |                          |
+-----------+-----------------+------+-----+---------+--------------------------+
3 rows in set (0.00 sec)--复制的列作为新增字段
SQL> CREATE TABLE t1 (a int) SELECT name,age FROM t2; 
Query OK, 3 rows affected (0.07 sec)
Records: 3  Duplicates: 0  Warnings: 0SQL> select * from t1;
+------+--------+-----+
| a    | name   | age |
+------+--------+-----+
| NULL | Joe    |  35 |
| NULL | Rachel |  31 |
| NULL | Monica |  33 |
+------+--------+-----+
3 rows in set (0.00 sec)--复制的不同列作为新增字段，同名的列被覆盖      
SQL> CREATE TABLE t1 (a int, name varchar(30)) SELECT name,age FROM t2; 
Query OK, 3 rows affected (0.07 sec)
Records: 3  Duplicates: 0  Warnings: 0SQL> select * from t1;
+------+--------+-----+
| a    | name   | age |
+------+--------+-----+
| NULL | Joe    |  35 |
| NULL | Rachel |  31 |
| NULL | Monica |  33 |
+------+--------+-----+
3 rows in set (0.00 sec)--为复制过来的字段定义约束
SQL> CREATE TABLE t1 (name varchar(40) not null default 'Tony') SELECT name,age FROM t2; 
Query OK, 3 rows affected (0.13 sec)
Records: 3  Duplicates: 0  Warnings: 0SQL> desc t1;
+-----------+-----------------+------+-----+---------+--------------------------+
| Field     | Type            | Null | Key | Default | Extra                    |
+-----------+-----------------+------+-----+---------+--------------------------+
| my_row_id | bigint unsigned | NO   | PRI | NULL    | auto_increment INVISIBLE |
| name      | varchar(40)     | NO   |     | Tony    |                          |
| age       | int             | NO   |     | NULL    |                          |
+-----------+-----------------+------+-----+---------+--------------------------+
3 rows in set (0.00 sec)--为复制过来的字段定义索引
SQL> CREATE TABLE t1 (unique(employ_id)) SELECT employ_id,name FROM t3;
Query OK, 3 rows affected (0.07 sec)
Records: 3  Duplicates: 0  Warnings: 0SQL> desc t1;
+-----------+-----------------+------+-----+---------+--------------------------+
| Field     | Type            | Null | Key | Default | Extra                    |
+-----------+-----------------+------+-----+---------+--------------------------+
| my_row_id | bigint unsigned | NO   | PRI | NULL    | auto_increment INVISIBLE |
| employ_id | int             | YES  | UNI | NULL    |                          |
| name      | varchar(30)     | YES  |     | NULL    |                          |
+-----------+-----------------+------+-----+---------+--------------------------+
3 rows in set (0.01 sec)