sql-server - 不允许在另一个计算列定义中使用计算列

Question

我得到不允许在另一个计算列中使用计算列
当我尝试在另一个计算域中使用一个计算域时的定义错误消息。有什么解决方法可以实现这一点吗？

计算域1

ALTER TABLE DBO.[ASSy] ADD [CALC STOCK NO] AS (

CASE 
WHEN isnull([DIRECTIONAL TREAD],'') ='YES RIGHT' THEN isnull([STOCK NO],'')+'R'
WHEN isnull([DIRECTIONAL TREAD],'') ='YES LEFT' THEN isnull([STOCK NO],'')+'L'
ELSE isnull([STOCK NO],'')
end 
)

下面是第二个计算域。当我执行脚本时，我得到

Msg 1759, Level 16, State 0, Line 5 Computed column 'CALC STOCK NO' in table 'ASSy' is not allowed to be used in another computed-column definition.

ALTER TABLE dbo.[ASSy] ADD [PN & DESCRIPTION] AS (ISNULL([CALC STOCK NO],'')+ ', '+ISNULL([TIRE SIZE],'')+', '+ ISNULL([BH SPEC],''))

Answer 1

根据 Computed Columns文档:

A computed column is computed from an expression that can use other columns in the same table. The expression can be a noncomputed column name, constant, function, and any combination of these connected by one or more operators. The expression cannot be a subquery.

一个计算列不能引用另一个计算列。您有以下选择:

创建第二个计算列，其中包含与第一个计算列(无法引用)相同的逻辑。

用普通列替换第一个计算列:

ALTER TABLE DBO.[ASSy] DROP COLUMN [CALC STOCK NO]
ALTER TABLE ADD [CALC STOCK NO] VARCHAR(100) NULL
UPDATE TABLE t
    SET [CALC STOCK NO] = 
        CASE 
        WHEN isnull([DIRECTIONAL TREAD],'') ='YES RIGHT' THEN isnull([STOCK NO],'')+'R'
        WHEN isnull([DIRECTIONAL TREAD],'') ='YES LEFT' THEN isnull([STOCK NO],'')+'L'
        ELSE isnull([STOCK NO],'')
        END
FROM [CALC STOCK NO] t

创建一个 VIEW在表格顶部并在其中实现您的第二列:

CREATE VIEW DBO.[vASSy]
AS
SELECT   t.*
        ,[PN & DESCRIPTION] = (ISNULL([CALC STOCK NO],'')+ ', '+ISNULL([TIRE SIZE],'')+', '+ ISNULL([BH SPEC],''))
FROM DBO.[ASSy] t