PostgreSQL
PostgreSQL
SELECT *
FROM a
FULL OUTER JOIN b ON a.k = b.k;MySQL 模拟
MySQL 模拟
SELECT * FROM a LEFT JOIN b ON a.k = b.k
UNION
SELECT * FROM a RIGHT JOIN b ON a.k = b.k;| 语义 | 左独有 + 匹配 + 右独有 |
|---|---|
| MySQL | 语法上不支持 FULL [OUTER] JOIN，需模拟 |
| 模拟细节 | UNION 会去重：两段都产出的匹配行合并为一份 |