An Error Was Encountered

Error Number: 1690

BIGINT UNSIGNED value is out of range in '(`p193169_mirplas`.`a`.`tLevel` - 1)'

SELECT a.ItemCategoryID AS id, a.Name, a.isAllowItems, b.ItemCategoryID AS parent_id, ( SELECT COUNT( * ) AS number FROM `itemlocation` il WHERE il.LocationID IN ( SELECT cat1.ItemCategoryID FROM itemcategory cat1, itemcategory cat2 WHERE cat2.ItemCategoryID = a.ItemCategoryID AND cat1.tLeft >= cat2.tLeft AND cat1.tRight <= cat2.tRight ) AND il.LocationTypeID =0 ) AS count_all_items FROM itemcategory a, itemcategory b WHERE a.tLeft BETWEEN b.tLeft AND b.tRight AND b.tLevel = a.tLevel -1 ORDER BY a.Name, a.tLeft