informatic从多张表取数、或多表关联
informatic从多张表取数、或多表关联
Join = select a.a from a, b where a.aa = b.aa
lookup = select a.a from a where exists (select 1 from b where a.aa=b.aa)
Join = select a.a from a, b where a.aa = b.aa
lookup = select a.a from a where exists (select 1 from b where a.aa=b.aa)