scalikejdbc - 如果不存在则插入

Question

如何在ScalikeJDBC QueryDSL中编写以下代码，或者通过ScalikeJDBC以最优雅的方式编写？

begin tran
if not exists (select * from T1 with (UPDLOCK) where c1=1 and c2=2 )
   insert into T1(c1,c2) values(1,2)
commit tran