SQL Server while loop union all [closed]

Answer 1

Instead of trying to use UNION I would use a temp table or temp table variable to merge the result sets

CREATE TABLE #Temp
(
  <COLUMNS>
)

 DECLARE @position INT
 SET @position = -1

 WHILE(@position < 1)
 BEGIN

    INSERT INTO #Temp (<COLUMNS>)
    SELECT * FROM mytable

    SET @position = @position + 1

 END

 SELECT * FROM #Temp

Answer 2

This way gets rid of the the UNION statement and avoids a loop altogether:

DECLARE @position INT
SET @position = 5

DECLARE @n TABLE (n int)

INSERT INTO @n 
SELECT ROW_NUMBER() OVER (ORDER BY name) AS x
FROM syscolumns

SELECT t.* 
FROM dbo.Table t
    CROSS JOIN @n n 
WHERE n <= @position    

Answer 3

You need a second set to UNION on. The while loop doesn't hold on to the selected set and know it the next time through. What you're trying to accomplish is basically select all the data from mytable then union it again on the same set...n times. Which really doesn't make sense. Remember that SQL is set based, so select * From mytable will select every record in there. You also never state what you're trying to accomplish.

Answer 4

That query makes no sense. To use UNION, you need to be selecting from a second table.

SQL Server essentially sees:

SELECT * FROM mytable      

UNION ALL 

With no second table after the UNION.