PostgreSQL: Select one of two fields depending on which is empty

Use CASE WHEN .. THEN .. ELSE .. END, e.g.:

SELECT (CASE WHEN (field1 IS NULL OR field1 = '') THEN field2 ELSE field1 END)FROM table;

sql postgresql syntax ternary-operator

SELECT COALESCE(NULLIF(field1, ''), field2) AS the_field FROM my_table;

sql postgresql syntax ternary-operator

The ANSI SQL function Coalesce() is what you want.

 select Coalesce(field1,field2) from   table;

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