INSTR Function

CREATE FUNCTION INSTR (
@inString VARCHAR(4000), 
@SearchStr VARCHAR(255),
@Position INT,
@Occurrence INT )
RETURNS INT
AS
BEGIN
DECLARE @retVal INT,@tempStr VARCHAR(4000),
 @strLen INT, @i INT, @tVal INT
SET @tempStr = sisi.SUBSTR(@inString,1,LEN(@inString) + @position)
SET @strLen = LEN(@tempStr)
IF @Occurrence <= 0
RETURN 0
ELSE
BEGIN
IF @strLen <= @Position OR @strLen <= @Occurrence or @position = 0
SET @retVal = 0
ELSE
BEGIN
IF @position < 0 
BEGIN
SET @Occurrence = LEN(REPLACE(@tempStr,@searchStr,@searchStr+';')) - LEN(@tempStr) - @Occurrence +1
IF @occurrence < 0 or @occurrence = 0
RETURN 0
ELSE IF @occurrence = 0
SET @occurrence = @occurrence
END
ELSE
BEGIN
SET @tempStr = sisi.SUBSTR(@inString,@Position,LEN(@inString))
IF @Occurrence > LEN(REPLACE(@tempStr,@searchStr,@searchStr+';')) - LEN(@tempStr) 
 RETURN 0
END

SET @i = 0

IF LEN(@tempStr) > 0 
BEGIN
IF @position > 1
SET @retVal = @position -1
ELSE
SET @retVal = 1
WHILE @i < @Occurrence
BEGIN
SET @retVal = CHARINDEX(@SearchStr,@tempStr,ISNULL(@tVal,1)) 
IF @retVal > 0
SET @tVal = @retVal +1
ELSE
SET @tVal = @retVal
SET @i = @i+1
END
END
END
END
IF @position > 0
SET @retVal = @retVal + @position-1
ELSE IF @position < 0
SET @retVal = @retVal 
RETURN @retVal
END