如何使用 SQL 将同一表和列上的值从一个 where 条件更新到另一个 where 条件

Question

我想在不同的 where 条件下更新列值。 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

我得到上面的费率值。 现在我想在不同的monthid条件下在同一个表中看到这些费率列值，如下所示

SELECT rate 
FROM dbo.sales 
WHERE monthid = 201611

更新后结果：

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

决赛桌：

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

是否可以将速率值从一个 where 条件更新到另一个 where 条件？

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

仅当您每个月只为每个产品记录一次时才有效。

Answer 2

这可能有助于更新速率值。

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

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

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

创建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