基於任何表中的值選擇列（列的數量是可變的）SQL

Question

我有如下表：

Table 1

而且我想只顯示50歲以下至少有一個值列：

Table 2

我需要一個存儲過程，做到這一點。訣竅是我想在多個表上使用它，但列的數量因表而異。

可以這樣做嗎？

Answer 1

希望這會有一些幫助。

SET NOCOUNT ON 

DECLARE 
    @tablename VARCHAR(50) = 'Table1', 
    @valuetocompare INT = 50, 
    @otherfields VARCHAR(100) = 'Date, Hour,'; 

DECLARE @t AS TABLE (cname VARCHAR(10), cvalue INT) 
DECLARE @sql NVARCHAR(1000); 
DECLARE @cname VARCHAR(128); 
DECLARE c CURSOR 
FOR 
    SELECT NAME 
    FROM sys.[columns] AS c 
    WHERE c.[object_id] = OBJECT_ID(@tablename) 
; 

OPEN c; 
FETCH NEXT FROM c INTO @cname; 

WHILE @@FETCH_STATUS = 0 
BEGIN 
    SET @sql = 'select ''' + @cname + ''', ' + @cname + ' from ' + @tablename; 

    INSERT INTO @t 
     (
     cname, 
     cvalue 
    ) 
    EXECUTE (@sql); 

    FETCH NEXT FROM c INTO @cname; 
END 

CLOSE c; 
DEALLOCATE c; 

DECLARE @cnames VARCHAR(100) = ''; 
WITH dcnames AS (
     SELECT DISTINCT cname 
     FROM @t 
     WHERE cvalue < @valuetocompare 
    ) 
SELECT @cnames = @cnames + cname + ',' 
FROM dcnames; 

IF @cnames = '' 
    PRINT 'No column value is less than ' + CAST(@valuetocompare AS VARCHAR); 
ELSE 
BEGIN 
     SET @sql = 'select ' + @otherfields + LEFT(@cnames, LEN(@cnames) - 1) + ' from ' + @tablename; 
     EXECUTE (@sql); 
END