using 等价于 join 操作中的 on,如:
SELECT id FROM table1 AS a
JOIN table2 AS b
ON a.id=b.id
等价于:
SELECT id FROM table1 AS a
JOIN table2 AS b
using(id)
using 等价于 join 操作中的 on,如:
SELECT id FROM table1 AS a
JOIN table2 AS b
ON a.id=b.id
等价于:
SELECT id FROM table1 AS a
JOIN table2 AS b
using(id)