常見SQL關聯查詢

1. inner join 內連接查詢

SELECT a.*,b.* FROM table_a a INNER JOIN table_b b ON a.id=b.id；

2. left join 左關聯查詢

SELECT a.*,b.* FROM table_a a LEFT JOIN table_b b ON a.id=b.id；

3.right join 右關聯查詢

SELECT a.*,b.* FROM table_a a RIGHT JOIN table_b b ON a.id=b.id；

4.左連接-內連接

SELECT a.*,b.* FROM table_a a LEFT JOIN table_b b ON a.id=b.id WHERE b.id IS NULL；

5. 右連接-內連接

SELECT a.*,b.* FROM table_a a RIGHT JOIN table_b b ON a.id=b.id WHERE a.id IS NULL