SET NOCOUNT ON;
DECLARE @TempStats TABLE (StatsName varchar(500));
DECLARE @StatsName varchar(500);
DECLARE @sql varchar(MAX);

INSERT INTO @TempStats
    (StatsName)
SELECT    
    OBJECT_NAME([object_id]) + '.' + [name]
FROM 
    sys.stats S
WHERE
    OBJECTPROPERTY([object_id], 'IsMSShipped') = 0 AND
    [NAME] LIKE '_WA_Sys%';

SELECT 
    @StatsName = MIN(StatsName)
FROM
    @TempStats;

WHILE @StatsName IS NOT NULL
BEGIN
    SELECT @sql = 'DROP STATISTICS ' + @StatsName;
    EXEC (@sql);
    
    PRINT 'Deleted statistics: ' + @StatsName;
    
    DELETE
        @TempStats
    WHERE
        StatsName = @StatsName;
        
    SELECT 
        @StatsName = MIN(StatsName)
    FROM
        @TempStats;
END