Monadic joins to SQL

gistfile1.txt

t1.flatMap(a => t2.filter(b => b.s == a.s).map(b => b.s))

  SELECT t2.s FROM t1, t2 WHERE t2.s = t1.s

t1.flatMap(a => t2.map(b => b.s).take(10))

  SELECT x.s FROM t1, (SELECT * FROM t2 LIMIT 10) x

t1.flatMap(a => t2.filter(b => b.s == a.s).map(b => b.s).take(10))

  Is it possible to translate this composition to SQL?
  

I've found one alternative, but it's not generic enough to cover other similar compositions:

SELECT x.s FROM t1, (SELECT t2.* from t2 WHERE EXISTS (SELECT * FROM t1 WHERE t2.s = t1.s) LIMIT 10)

The normalized composition would be:

t1.flatMap(a => t2.filter(b => t1.filter(b.s == a.s).nonEmpty).take(10))

Example of composition that can't be normalized using this approach:

t1.flatMap(a => t2.filter(b => b.s == a.s).sortBy(b => a.s).take(10))