使用连接的SQL更新查询
我必须更新一个由3个表连接返回的值的字段。
例：
select
im.itemid
,im.sku as iSku
,gm.SKU as GSKU
,mm.ManufacturerId as ManuId
,mm.ManufacturerName
,im.mf_item_number
,mm.ManufacturerID
from
item_master im, group_master gm, Manufacturer_Master mm
where
im.mf_item_number like 'STA%'
and im.sku=gm.sku
and gm.ManufacturerID = mm.ManufacturerID
and gm.manufacturerID=34
我想用上面条件中加入的其他一些值更新表item_master的mf_item_number字段值。
我如何在MS SQL Server中执行此操作？
UPDATE im
SET mf_item_number = gm.SKU --etc
FROM item_master im
JOIN group_master gm
ON im.sku = gm.sku
JOIN Manufacturer_Master mm
ON gm.ManufacturerID = mm.ManufacturerID
WHERE im.mf_item_number like 'STA%' AND
gm.manufacturerID = 34
为了清楚起见...... UPDATE子句可以引用在FROM子句中指定的表别名。 所以im在这种情况下是有效的
通用示例
UPDATE A
SET foo = B.bar
FROM TableA A
JOIN TableB B
ON A.col1 = B.colx
WHERE ...
最简单的方法之一是使用公用表表达式（因为您已经在SQL 2005上）：
with cte as (
select
im.itemid
,im.sku as iSku
,gm.SKU as GSKU
,mm.ManufacturerId as ManuId
,mm.ManufacturerName
,im.mf_item_number
,mm.ManufacturerID
, <your other field>
from
item_master im, group_master gm, Manufacturer_Master mm
where
im.mf_item_number like 'STA%'
and im.sku=gm.sku
and gm.ManufacturerID = mm.ManufacturerID
and gm.manufacturerID=34)
update cte set mf_item_number = <your other field>
查询执行引擎将自行解决如何更新记录。
将它适配到MySQL - 在UPDATE没有FROM子句，但是这起作用：
UPDATE
item_master im
JOIN
group_master gm ON im.sku=gm.sku
JOIN
Manufacturer_Master mm ON gm.ManufacturerID=mm.ManufacturerID
SET
im.mf_item_number = gm.SKU --etc
WHERE
im.mf_item_number like 'STA%'
AND
gm.manufacturerID=34