如何在sql循環中執行

Question

我需要執行循環，直到@ss返回null或數字「 - 」。所以嘗試了下面的代碼

DECLARE @i int,@ss varchar(20) 
SET @i=1; 
--WHILE (@ss =null) 
WHILE(@i<=3)// i need to assign i value dynamically 
BEGIN 
SET @ss =(SELECT dbo.GetStringPart('-','hello-world',@i)) 
PRINT @ss 
SET @i =@i+1 
END 

功能：GetStringPart

ALTER FUNCTION [dbo].[GetStringPart] (@sep varchar(1), @s varchar(512),@pos int) 
RETURNS VARCHAR(200) 
AS 
BEGIN 
DECLARE @output VARCHAR(200) 
;WITH Pieces(pn, start, stop) AS (
    SELECT 1, 1, CHARINDEX(@sep, @s) 
    UNION ALL 
    SELECT pn + 1, stop + 1, CHARINDEX(@sep, @s, stop + 1) 
    FROM Pieces 
    WHERE stop > 0 
) 
SELECT 
    @output=SUBSTRING(@s, start, CASE WHEN stop > 0 THEN stop-start ELSE 512 END) 
FROM Pieces 
WHERE pn=@pos 
RETURN @Output 
END 

怎麼辦it.thanks ...

Answer 1

使用IS和IS NOT代替=和<>與NULL進行比較：

WHILE @ss IS NOT NULL 

哦，讓循環會在第一時間，給@ss虛擬初始化：

DECLARE @i int, @ss varchar(20) = ''