将多个 CASE 语句合并为一个并 SELECT INTO 临时表

Question

我有一个产生单独输出的查询。我需要将 SELECT CASE 语句合并为一个，然后将所有输出插入到临时表中

SELECT CASE WHEN #WCV_3.VISIT_1 IS NULL THEN '' ELSE CONVERT(VARCHAR(10), #WCV_3.VISIT_1,110) END
FROM #WCV_3

SELECT CASE WHEN #WCV_3.VISIT_2 IS NULL THEN '' ELSE CONVERT(VARCHAR(10), #WCV_3.VISIT_2,110) END
FROM #WCV_3

等等……

SELECT CASE WHEN #WCV_3.VISIT_5 IS NULL THEN '' ELSE CONVERT(VARCHAR(10), 
 #WCV_3.VISIT_5, 110) END
FROM #WCV_3

我试过了

SELECT * INTO
 #WCV_4 (this is my new temp table)
FROM
(
SELECT CASE WHEN #WCV_3.VISIT_1 IS NULL THEN '' ELSE CONVERT(VARCHAR(10), #WCV_3.VISIT_1,110) END
FROM #WCV_3
etc... END)

但出现2个错误：

“关键字'SELECT'附近的语法不正确”

与

“')'附近的语法不正确”

`

Answer 1

您的查询应如下所示：

SELECT SomeColumn 
INTO #WCV_4
FROM (
    SELECT CASE WHEN #WCV_3.VISIT_1 IS NULL THEN '' ELSE CONVERT(VARCHAR(10), #WCV_3.VISIT_1,110) END AS SomeColumn FROM #WCV_3
    UNION ALL
    SELECT CASE WHEN #WCV_3.VISIT_2 IS NULL THEN '' ELSE CONVERT(VARCHAR(10), #WCV_3.VISIT_2,110) END AS SomeColumn FROM #WCV_3
    UNION ALL
    SELECT CASE WHEN #WCV_3.VISIT_4 IS NULL THEN '' ELSE CONVERT(VARCHAR(10), #WCV_3.VISIT_4, 110) END AS SomeColumn FROM #WCV_3
    UNION ALL
    SELECT CASE WHEN #WCV_3.VISIT_5 IS NULL THEN '' ELSE CONVERT(VARCHAR(10), #WCV_3.VISIT_5, 110) END AS SomeColumn FROM #WCV_3
) AS temp

Combines the results of two or more queries into a single result set that includes all the rows that belong to all queries in the union.

更多信息可以在这里找到http://msdn.microsoft.com/en-us/library/ms180026.aspx

我已经测试了这个查询（没有#WCV_3 表）并且它有效：

SELECT SomeColumn 
INTO #WCV_4
FROM (
    SELECT CASE WHEN 'a' IS NULL THEN '' ELSE CONVERT(VARCHAR(10), 'a',110) END AS SomeColumn
    UNION ALL
    SELECT CASE WHEN 'a' IS NULL THEN '' ELSE CONVERT(VARCHAR(10), 'a',110) END AS SomeColumn
    UNION ALL
    SELECT CASE WHEN 'a' IS NULL THEN '' ELSE CONVERT(VARCHAR(10), 'a', 110) END AS SomeColumn
    UNION ALL
    SELECT CASE WHEN 'a' IS NULL THEN '' ELSE CONVERT(VARCHAR(10), 'a', 110) END AS SomeColumn
) AS temp