我正在尝试比较来自不同表的数据,插入新数据,以及更新不匹配的数据.
例：
I have table1 ------------------------------------ | ITEMNO | DESCRIPTION | FORSALE | ------------------------------------ | 123456 | Description1 | YES | ------------------------------------ | 234567 | Description2 | YES | ------------------------------------ | 345678 | Description3 | YES | ------------------------------------
我也有table2,它只是一个临时表
---------- | ITEMNO | ---------- | 123456 | ---------- | 234567 | ----------
ITEMNO是表1中的主键和表2中的外键
因此,当程序中的模块发送数据时,它将首先检查table2,然后将数据与表1进行比较
如果发送的数据是这样的
table2 table1
---------- ----------
| ITEMNO | | ITEMNO |
---------- ----------
| 123456 | = | 123456 | (MATCH WITH TABLE1 AND TABLE2 THEN UPDATE)
---------- ----------
| 234567 | = | 234567 | (MATCH WITH TABLE1 AND TABLE2 THEN UPDATE)
---------- ----------
| 567890 | = | 567890 | (NEW DATA THEN INSERT INTO TABLE 1)
---------- ----------
| 345678 | (DOESN'T EXIST IN TABLE2 BUT EXISTS IN TABLE 1 SO UPDATE FORSALE FIELD TO "NO")
----------
任何帮助将不胜感激,在此先感谢.
解决方法:
您可以通过低于2 sql-实现它
UPDATE table1 AS t1
LEFT JOIN table2 AS t2 ON t1.itemno=t2.itemno
SET t1.FORSALE='No'
WHERE t2.itemno IS NULL;
INSERT IGnorE INTO table2 (itemno) SELECT t1.itemno
FROM table1 AS t1
LEFT JOIN table2 AS t2 ON t1.itemno=t2.itemno
WHERE t2.itemno IS NULL;
但更好的选择是使用存储过程,它将首先从下面的查询中获取未匹配的itemno并将其保存在游标中然后根据主键更新和插入,因为它可以避免锁定 –
SELECT t1.itemno
FROM table1 AS t1
LEFT JOIN table2 AS t2 ON t1.itemno=t2.itemno
WHERE t2.itemno IS NULL;
