如何将另一行的值插入到列中 - SQL 服务器

Question

我正在为一个项目SQL工作，我需要根据一些规则更新Soh_Wh_A和Soh_Wh_B。

这是table_A:

| Code  | Warehouse | StockOnHand | Wh_A     | Wh_B 
----------------------------------------------------
| 001   | A         | 10          | NULL     | NULL     
| 001   | B         | 20          | NULL     | NULL     
| 003   | A         | 30          | NULL     | NULL     
| 033   | B         | 40          | NULL     | NULL

我想填充列 Wh_A 和 Wh_B。例如，让我们处理第一行，Wh_A 应该具有与列 StockOnHand 相同的值，因为该行属于仓库“A”。使用 update case when 语句很容易做到这一点。

对我来说困难的是用第二行的 StockOnHand 列填充 Wh_B 列。

最后的table应该是这样的

| Code  | Warehouse | StockOnHand | Wh_A     | Wh_B 
----------------------------------------------------
| 001   | A         | 10          | 10       | 20
| 001   | B         | 20          | 10       | 20
| 003   | A         | 30          | 30       | 40     
| 033   | B         | 40          | 30       | 40

这是我到目前为止所做的...

update Table_A set
Wh_A = (case 
        when warehouse = 'A' then stockOnHand
        when warehouse = 'B' then ... end)
Wh_B = (case 
        when warehouse = 'A' then stockOnHand
        when warehouse = 'B' then ... end)

Answer 1

declare @Table table (
    Code        char(3) not null,
    Warehouse   char(1) not null,
    StockOnHand int     not null,
    Wh_A        int         null,
    Wh_B        int         null,

    primary key (Code, Warehouse)
);

insert into @Table
    (Code, Warehouse, StockOnHand)
values 
    ('001', 'A', 10), 
    ('001', 'B', 20), 
    ('003', 'A', 30), 
    ('003', 'B', 40);

update t set
    Wh_A = (select top 1 StockOnHand from @Table a where a.Warehouse = 'A' and a.Code = t.Code),
    Wh_B = (select top 1 StockOnHand from @Table b where b.Warehouse = 'B' and b.Code = t.Code)
from 
    @Table t;


select * from @Table

Answer 2

您可以使用 window 函数：

select 
    code,
    warehouse,
    stockOnHand,
    max(case when warehouse = 'A' then stockOnHand end)
        over(partition by code) wh_a,
    max(case when warehouse = 'B' then stockOnHand end)
        over(partition by code) wh_b
from table_a

使用可更新的 cte 很容易将其转换为 update 查询：

with cte as (
    select 
        wh_a,
        wh_b
        max(case when warehouse = 'A' then stockOnHand end)
            over(partition by code) new_wh_a,
        max(case when warehouse = 'B' then stockOnHand end)
            over(partition by code) new_wh_b
    from table_a
)
update cte set wh_a = new_wh_a, wh_b = new_wh_b

如何将另一行的值插入到列中 - SQL 服务器

How to insert a value from another row into a column - SQL Server

sql

sql-server

common-table-expression

window-functions

sql-update