how to use REGEXP

[zhenghongyi]

let levelPathExp = SQLite.Expression<String?>("levelPath")
tables.organizations.filter(levelPathExp.like("\(fatherLevelPath)/%"))

i use above to query my datas, it works. but when i use below, it don`t work

let levelPathExp = SQLite.Expression<String?>("levelPath")
tables.organizations.filter(levelPathExp.regexp("^\(fatherLevelPath)/[^/]+"))

the error is "no such function: REGEXP". Can anybody tell me how to use REGEXP? ths