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Create view from not empty table postgresql

Time：09-22

everyone!

I have 2 tables: t1 and t2. They are almost the same (by column), but in different schemes s1 and s2.

So I need to create view from t1 if it not empty or from t2 (if t1 empty).

Example:

s1.t1.  s2.t2
1        2
2       10
3        2

view:
1
2
3

Second:

s1.t1.    s2.t2
<empty>.    1
            2
            9

View:
1
2
9

CodePudding user response：

The query could be

SELECT * FROM t1
UNION ALL
SELECT * FROM t2
   WHERE NOT EXISTS (SELECT 1 FROM t1);