sql-server - 是否可以在 SQL 中选择一个 select 而无需创建 nvarchar 变量？

Question

我正在尝试做这样的事情:

--This table has a list of columns I need from #testTableTwo
CREATE TABLE #testTableOne
(
    id  nvarchar(250)
)

--This column has the values I need. I just don't know which columns I want.
CREATE TABLE #testTableTwo
(
    one INT,
    two INT,
    three INT,
    four int
)



INSERT INTO #testTableOne VALUES ('one'),('two'),('three')
INSERT INTO #testTableTwo VALUES (1,2,3,4)
    SELECT (SELECT * FROM #testTableOne) FROM #testTableTwo

所以我想要的是:

SELECT ONE, TWO, THREE FROM #testTableTwo

这可能吗？我知道我可以制作一个 nvarchar 并使用 COALESCE 做一些事情，但我试图避免这种情况。有什么好的办法吗？

Answer 1

您必须像这样使用动态 SQL。

-- First construct the fields list
DECLARE @fields varchar(500)
SET @fields = STUFF((SELECT ', ' + #testTableOne.id
                FROM #testTableOne
                FOR XML PATH(''),TYPE).value('.','VARCHAR(MAX)')
            , 1, 2, '')

-- Next construct the actual SQL statement
DECLARE @sql nvarchar(max)
SET @sql = 'SELECT '+@fields+' FROM #testTableTwo'

-- And last but not least run it.
EXEC sp_executesql @sql