如何使用 SQL 將同一表和列上的值從一個 where 條件更新到另一個 where 條件

Question

我想在不同的 where 條件下更新列值。 下面是例子

ID,  Product,   MonthID,  Rate
1 ,     a,      201610,    13
2 ,     a,      201611,    22
3 ,     b,      201610,    29
4 ,     b,      201611,    14

SELECT rate 
FROM dbo.sales 
WHERE monthid = 201610

ID,  Product,  MonthID,  Rate
 1,     a,     201610,    13
 3,     b,     201610,    29

我得到上面的費率值。 現在我想在不同的monthid條件下在同一個表中看到這些費率列值，如下所示

SELECT rate 
FROM dbo.sales 
WHERE monthid = 201611

更新后結果：

ID,  Product,  MonthID,   Rate
 2,     a,     201611,     13
 4,     b,     201611,     29

決賽桌：

ID,  Product,   MonthID,   Rate
 1,     a,      201610,     13
 2,     a,      201611,     13
 3,     b,      201610,     29
 4,     b,      201611,     29

是否可以將速率值從一個 where 條件更新到另一個 where 條件？

Answer 1

update s
set rate = (select rate from dbo.sale where idmonth = 201610 and product = a.product )
from dbo.sales s 
where idmonth = 201611

僅當您每個月只為每個產品記錄一次時才有效。

Answer 2

這可能有助於更新速率值。

update s1
    set s1.rate = s2.rate
from sales s2 (nolock)
inner join sales s1
    on s1.MonthID = s2.MonthID + 1 and s1.Product = s2.Product
where s2.MonthID = 201610

Answer 3

創建 V1（在 sql 中查看）：SELECT id, Product, MonthID, Rate FROM dbo.tb1 WHERE (MonthID = 201610)

創建 V2（在 sql 中查看）：SELECT id, Product, MonthID, Rate FROM dbo.tb1 WHERE (MonthID = 201611)

創建V3（在sql中查看）：SELECT dbo.V1.id, dbo.V1.Product, dbo.V1.MonthID, dbo.V1.Rate, dbo.V2.id AS id2, dbo.V2.Product AS Product2, dbo .V2.MonthID AS MonthID2, dbo.V2.Rate AS Rate2 FROM dbo.V1 INNER JOIN dbo.V2 ON dbo.V1.Product = dbo.V2.Product GROUP BY dbo.V1.id, dbo.V1.Product, dbo .V1.MonthID、dbo.V1.Rate、dbo.V2.id、dbo.V2.Product、dbo.V2.MonthID、dbo.V2.Rate

id Product MonthID Rate id2 Product2 MonthID2 Rate2 1 a 201610 13 2 a 201611 22 3 b 201610 29 4 b 201611 14