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)

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: 0mysql> 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)

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: 0mysql> select * from producttype;
+----+--------+
| ID | amount |
+----+--------+
|  1 |     10 |
|  2 |   NULL |
|  3 |   NULL |
+----+--------+
3 rows in set (0.00 sec)

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

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

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;