MySQL更新命令_UPDATE

创建测试表

mysql> CREATE TABLE `product` (
    ->    `proID` int(11) NOT NULL AUTO_INCREMENT COMMENT '商品表主键',
    ->    `price` decimal(10,2) NOT NULL COMMENT '商品价格',
    ->    `type` int(11) NOT NULL COMMENT '商品类别(0生鲜,1食品,2生活)',
    ->    `dtime` datetime NOT NULL COMMENT '创建时间',
    ->    PRIMARY KEY (`proID`)
    ->  ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8 COMMENT='商品表';
Query OK, 0 rows affected (0.11 sec)

mysql> CREATE TABLE `producttype` (
    ->    `ID` int(11) NOT NULL COMMENT '商品类别(0生鲜,1食品,2生活)',
    ->    `amount` int(11)  COMMENT '每种类别商品总金额',
    ->    UNIQUE KEY (`ID`)
    ->  ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='商品类别资金汇总表'
    -> ;
Query OK, 0 rows affected (0.12 sec)

　mysql> INSERT INTO product(price,type,dtime) VALUES(10.00,0,now()),(10.00,1,now()),(10.00,1,now()),(20.00,2,now()),(30.00,3,now());
　Query OK, 5 rows affected (0.06 sec)
　Records: 5 Duplicates: 0 Warnings: 0

　mysql> INSERT INTO producttype(ID) VALUES(1),(2),(3);
　Query OK, 3 rows affected (0.04 sec)
　Records: 3 Duplicates: 0 Warnings: 0

mysql> select * from product;
+-------+-------+------+---------------------+
| proID | price | type | dtime               |
+-------+-------+------+---------------------+
|     1 | 10.00 |    0 | 2018-01-31 03:06:05 |
|     2 | 10.00 |    1 | 2018-01-31 03:06:05 |
|     3 | 10.00 |    1 | 2018-01-31 03:06:05 |
|     4 | 20.00 |    2 | 2018-01-31 03:06:05 |
|     5 | 30.00 |    3 | 2018-01-31 03:06:05 |
+-------+-------+------+---------------------+
5 rows in set (0.00 sec)

mysql> select * from producttype;
+----+--------+
| ID | amount |
+----+--------+
|  1 |   NULL |
|  2 |   NULL |
|  3 |   NULL |
+----+--------+
3 rows in set (0.00 sec)

1. 单表更新

UPDATE用法：update 表名 set  属性1=value1,属性2=value2 where 限定条件

示例：

mysql> UPDATE product
    -> SET price='20.00',type=0 
    -> WHERE proID=2;
Query OK, 1 row affected (0.04 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from product;
+-------+-------+------+---------------------+
| proID | price | type | dtime               |
+-------+-------+------+---------------------+
|     1 | 10.00 |    0 | 2018-01-31 03:06:05 |
|     2 | 20.00 |    0 | 2018-01-31 03:06:05 |
|     3 | 10.00 |    1 | 2018-01-31 03:06:05 |
|     4 | 20.00 |    2 | 2018-01-31 03:06:05 |
|     5 | 30.00 |    3 | 2018-01-31 03:06:05 |
+-------+-------+------+---------------------+
5 rows in set (0.00 sec)

2. 关联更新

UPDATE用法：update 表名1,表名2 set  表1.属性=表2.属性值 where 限定条件

示例：

mysql> UPDATE producttype,product
    -> SET producttype.amount=product.price
    -> where product.TYPE = producttype.ID AND product.TYPE=1;
Query OK, 1 row affected (0.09 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from producttype;
+----+--------+
| ID | amount |
+----+--------+
|  1 |     10 |
|  2 |   NULL |
|  3 |   NULL |
+----+--------+
3 rows in set (0.00 sec)

3. 限制更新

UPDATE用法：update 表名1,表名2 set  表1.属性=表2.属性值 where 限定条件 limit  m

说明：只支持更新前多少行，而不支持非TOP的指定范围更新，也就是说，limit只接收一个参数。

意义：更新前m个符合where条件的记录。

mysql> UPDATE tb_name SET column_name='test' LIMIT 30;

4. 排序更新

UPDATE用法：update 表名1,表名2 set  表1.属性=表2.属性值 where 限定条件 order by ... [limit m]

说明：同限制更新一样，首先判断出符合where条件的记录，然后对符合条件的记录进行排序，最后对排序后的前m条记录做更新

mysql> UPDATE tb_name SET column_name='test' ORDER BY id ASC LIMIT 30;

5. 联合更新

UPDATE用法：update 表A set  A.属性=表B.属性值 FROM a as A [inner join | right join | left join] b as B on [连接条件] where 限定条件

mysql> UPDATE Table_A
    -> SET Table_A.col1 = Table_B.col1,    
    ->  Table_A.col2 = Table_B.col2
    -> FROM Some_Table AS Table_A    
    -> INNER JOIN Other_Table AS Table_B ON Table_A.id = Table_B.id
    -> WHERE Table_A.col3 = 'cool';

mysql> update a  join b on a.id=b.id set a.name=b.name where a.year=2016;