所有时候都使用联合，一次只获得两列

Question

每次仅获得两列时，我都无法获取团队ID和user_type

SELECT `dev_user`.first_name,`dev_user`.user_id FROM `dev_test_teams_athlete` LEFT JOIN dev_user ON dev_test_teams_athlete.user_id = dev_user.user_id UNION ALL SELECT `dev_user`.first_name, `dev_test_team`.user_id as coach_id FROM `dev_user` RIGHT JOIN dev_test_team ON dev_test_team.user_id = dev_user.user_id UNION ALL SELECT dev_test_team.team_id,dev_test_teams_athlete.user_id as athlete FROM `dev_test_team` LEFT JOIN `dev_test_teams_athlete` ON `dev_test_team`.`team_id` = `dev_test_teams_athlete`.`team_id`

这是在查询中使用全部联盟关键字

的结果

我得到的结果类似不需要的结果enter image description here

我的dev_test_team表是enter image description here

我的dev_test_teams_athlete表是enter image description here

我的dev_user表是enter image description here

最后，我要得到图像enter image description here

中所述的结果

第一个我想这样回答

-------------------------------------------
    user_id | first_name | user_type | team_id
    -------------------------------------------
    480         coach1       3          1
    472         coach2       3          2
    465         coach3       3          3

    380         athlete1     4          1 
    375         athlete2     4          2
    479         athlete3     4          3
    464         athlete4     4          3

Answer 1

SELECT
    `x`.`team_id`, `du`.`first_name`, `du`.`user_type`, `x`.`team_id`
FROM(
    SELECT `team_id`, `user_id` FROM `dev_test_team`

    UNION ALL

    SELECT `team_id`, `user_id` FROM `dev_test_teams_athlete`
) `x`
LEFT JOIN `dev_user` `du` ON `du`.`user_id` = `x`.`user_id`

================================================ ============

尝试一下。