G select * from t1 left join t3 on t1.f1 = t3.f1 left join t2 on t1.f1 = t2.f1; (with normalized outer joins) cluster0 Box0:Select cluster1 Box1:OuterJoin cluster5 Box5:BaseTable T2 cluster2 Box2:OuterJoin cluster4 Box4:BaseTable T3 cluster3 Box3:BaseTable T1 boxhead0 Distinct: Preserve 0: Q4.c0 as F1 1: Q4.c1 as F2 2: Q4.c2 as F3 3: Q0.c0 as F1 4: Q0.c1 as F2 5: Q0.c2 as F3 6: Q2.c0 as F1 7: Q2.c1 as F2 8: Q2.c2 as F3 Q0 Q0(F) boxhead1 Distinct: Preserve 0: Q3.c0 as F1 1: Q3.c1 as F2 3: Q3.c2 as F3 Q0->boxhead1 Q2 Q2(F) boxhead2 Distinct: Preserve 0: Q1.c0 as F1 1: Q1.c1 as F2 2: Q1.c2 as F3 Q2->boxhead2 Q4 Q4(F) Q3 Q3(F) as T2 Q4->Q3 (Q4.c0) = (Q3.c0) Q1 Q1(F) as T3 Q4->Q1 (Q4.c0) = (Q1.c0) boxhead3 Distinct: Preserve 0: c0 as F1 1: c1 as F2 2: c2 as F3 Q4->boxhead3 boxhead5 Distinct: Preserve 0: c0 as F1 1: c1 as F2 2: c2 as F3 Q3->boxhead5 boxhead4 Distinct: Preserve 0: c0 as F1 1: c1 as F2 2: c2 as F3 Q1->boxhead4