Is there a way to force join conditions in queries i.e. When a join is
made to a table on a particular field, another column should also be
checked?
CREATE TABLE test (info_type varchar(3), info_reference integer);
(depending on info_type, info_reference will contain key values from
different tables)
INSERT INTO test (info_type, info_reference) values ('abc','111'); ---
111 from tableA
INSERT INTO test (info_type, info_reference) values ('def','101');
--- 101 from tableB
INSERT INTO test (info_type, info_reference) values ('abc','119'); ---
119 from tableA
INSERT INTO test (info_type, info_reference) values ('def','103');
--- 103 from tableB
INSERT INTO test (info_type, info_reference) values ('def','104');
--- 104 from tableB
INSERT INTO test (info_type, info_reference) values ('def','105');
--- 105 from tableB
INSERT INTO test (info_type, info_reference) values ('def','111');
--- 111 from tableB
Now when joining tableA or tableB with test, joining only
info_reference will be wrong, we should also mention the info_type
value.
1. Is this an appropriate design for this requirement?
2. Is there a way to enforce the dual condition checking on all
queries. If a join is made to info_reference, info_type should also be
specified?
Thanks.
Ma Sivakumar
--
மா சிவகுமார்
எல்லோரும் எல்லாமும் பெற வேண்டும்
http://masivakumar.blogspot.com
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TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
