Very slow sql query using while loop and like select

I have the attached SQL query which taking hours to run. It badly needs optimising but I'm no SQL expert!
Any help greatly appreciated!

I think it's the like bit which is slowing the query down as the query strings table is massive.

Thanks,
Tristan

DECLARE @StartTime		DATETIME
DECLARE @EndTime		DATETIME
DECLARE @CatStart		INT
DECLARE @CatEnd			INT
DECLARE @TheDay			DATETIME
DECLARE @TheDayPlusOne	DATETIME
DECLARE @TheCat			INT
DECLARE @Count			INT
DECLARE @Search			VARCHAR(10)
 
SET @StartTime =		'April 17 2008'
SET @EndTime =			'June 17 2008'
SET @CatStart =			1
SET @CatEnd =			11
SET @TheDay =			@startTime
SET @TheDayPlusOne =	        DATEADD(DAY, 1, @TheDay)
SET @TheCat =			@CatStart
 
SET NOCOUNT ON
WHILE @TheDay < @endTime
BEGIN
	WHILE @TheCat < @CatEnd
	BEGIN
		SET @Search =	'%cat=' + CAST(@TheCat AS VARCHAR) + '%'
		SET @Count =	( 
		
		SELECT COUNT (DISTINCT WS.[UNIQUE_IDENTIFIER_ID]) 
		FROM [WAP_SESSIONS] AS WS
		INNER JOIN [PAGE_HITS] AS PH ON WS.[WAP_SESSION_ID] = PH.[WAP_SESSION_ID]
		INNER JOIN [QUERY_STRINGS] AS QS ON PH.[QUERY_STRING_ID] = QS.[QUERY_STRING_ID]
		WHERE QS.[QUERY_STRING] LIKE @Search
		AND WS.[CLIENT_ID] = 50510
		AND WS.[DATE_CREATED] BETWEEN @TheDay AND @TheDayPlusOne
 
		 )
 
		PRINT CAST(@TheCat AS VARCHAR) + ', ' + CAST(@TheDay AS VARCHAR) + ', ' + CAST (@Count AS VARCHAR)
		SET @TheCat =	@TheCat + 1		
	END
	SET @TheCat =		@CatStart
    SET @TheDay =		DATEADD(DAY, 1, @TheDay)
	SET @TheDayPlusOne =DATEADD(DAY, 1, @TheDay)
END
 
SET NOCOUNT OFF

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