SQL/MX 2.x Query Guide (H06.04+, J06.03+)

SQL/MX Operators
HP NonStop SQL/MX Query Guide—540437-005
7-34
LEFT_MERGE_JOIN Operator
The LEFT_HYBRID_HASH_JOIN operator has two child nodes. The description field
for this operator contains:
The example of the LEFT_HYBRID_HASH_JOIN operator is based on:
control query default nested_joins 'off';
prepare TestQuery37a from
SELECT *
FROM customer LEFT JOIN nation ON c_nationkey = n_nationkey
WHERE c_custkey > 1000 AND c_custkey < 1010
ORDER BY c_custkey;
DESCRIPTION
fragment_id ............ 0
parent_frag ............ (none)
fragment_type .......... master
join_type .............. left
join_method ............ hash
hash_join_predicate .... (DETCAT.DETSCH.CUSTOMER.C_NATIONKEY =
DETCAT.DETSCH.NATION.N_NATIONKEY)
LEFT_MERGE_JOIN Operator
Join Group
The LEFT_MERGE_JOIN operator describes a portion of an execution plan that
involves a merge join. The LEFT_MERGE_JOIN differs from MERGE_JOIN only when
it does not find a match in the inner table. When no match is found, the left row is still
Token Followed by ... Data Type
fragment_id A sequential number assigned to the
fragment. 0 is always the master executor
and 1 is reserved for the EXPLAIN plan.
Numbers 2 to n will be ESP or DAM
fragments.
integer
parent_frag The fragment_id for the parent fragment of
the current fragment. The value is (none)
for the master executor.
integer
fragment_type Master, ESP, or DP2. text
join_type Inner, left, natural, inner semi, or inner anti-
semi-join.
text
join_method Name of join method: hash text
hash_join_predicate Expression of the join predicate. expr(text)
parallel_join_type Type1 or Type2, depending on parallel join
algorithm.
text
selection_predicates Expression of the WHERE clause. expr(text)