PostgreSQL 知足條件時插入數據

例如：當表中不存在某記錄時，才插入這條記錄。

INSERT INTO 表名(列名1, 列名2)
SELECT
    '值1', '值2'
WHERE NOT EXISTS (
    SELECT * FROM 表名 WHERE 列名1 = '值1', 列名2 = '值2'
);

參考

1. PostgreSQL: Documentation: 10: INSERT

   This example inserts some rows into table films from a table tmp_films with the same column layout as films:

   INSERT INTO films SELECT * FROM tmp_films WHERE date_prod < '2004-05-07';

2. database - Conditional INSERT INTO statement in postgres - Stack Overflow