Specifies a merge join of two derived tables.
( m_g_join ( ( derived_table1 ) ( derived_table2 ) )
are the derived tables to be united. derived_table1 is always the outer table and derived_table2 is the inner table
A derived table that is the join of the specified derived tables.
select t1.c11, t2.c21 from t1, t2, t3 where t1.c11 = t2.c21 and t1.c11 = t3.c31
( nl_g_join ( m_g_join ( i_scan i_c31 t3 ) ( i_scan i_c11 t1 ) ) ( t_scan t2 ) )
Specifies a right-merge join of tables t1 and t3, followed by a nested-loop join with table t2.
select * from t1, t2, t3 where t1.c11 = t2.c21 and t1.c11 = t3.c31 and t2.c22 =7
( nl_g_join ( m_g_join ( i_scan i_c21 t2 ) ( i_scan i_c11 t1 ) ) ( i_scan i_c31 t3 ) )
Specifies a full-merge join of tables t2 (outer) and t1 (inner), followed in the join order by a nested-loop join with t3.
select c11, c22, c32 from t1, t2, t3 where t1.c11 = t2.c21 and t2.c22 = t3.c32
( m_g_join (nl_g_join (i_scan i_c11 t1) (i_scan i_c12 t2) ) (i_scan i_c32_ix t3) )
Specifies a nested-loop join of t1 and t2, followed by a merge join with t3.
The tables are joined in the order specified in the m_g_join clause.
The sort step and worktable required to process sort-merge join queries are not represented in abstract plans.
If the m_g_join operator is used to specify a join that cannot be performed as a merge join, the specification is silently ignored.