mysql的笔记

三张表，user表和role表和user_role表

我用了and查的，之后脑子想用左连接查，想不出来，只要敲一下，做个笔记

SELECT
  r.*
FROM
  t_user u,
  t_role r,
  t_user_role ur
WHERE u.`id` = ur.`user_id`
  AND r.`id` = ur.`role_id`
  AND u.`id` = 1;

SELECT
  r.*
FROM
  t_user u
  LEFT JOIN t_user_role ur
    ON u.`id` = ur.`user_id`
  LEFT JOIN t_role r
    ON ur.`role_id` = r.`id`
WHERE u.`id` = 1;