Question

如何仅对邀请表使用子查询？我希望来自patient_profiles的所有记录以及邀请加入时仅使用在特定日期之后创建的记录？

SELECT p.first_name,
COUNT(invites.invited_by_id)as invite_count
FROM patient_profiles AS p
LEFT OUTER JOIN patient_profiles AS invites ON invites.invited_by_id = p.id
WHERE p.is_test = false AND AND invites.created_at >= '2017-10-16'::date 
GROUP BY p.first_name

Answer 1

您不需要子查询。只需将日期条件移至ON子句：

SELECT p.first_name,
       COUNT(invites.invited_by_id)as invite_count
FROM patient_profiles p LEFT OUTER JOIN
     patient_profiles invite
     ON invites.invited_by_id = p.id AND invites.created_at >= '2017-10-16'::date
WHERE p.is_test = false
GROUP BY p.first_name;

Answer 2

您可以使用HAVING。

SELECT p.first_name, COUNT(invites.invited_by_id)as invite_count
FROM patient_profiles p
GROUP BY p.first_name
HAVING p.is_test = false AND p.created_at >= '2017-10-16'::date

SQL多表连接子查询

2 个答案: