[英]SQL: list users with their phone numbers and email addresses
我想在PostgreSQL中查询,列出我的用户及其电子邮件地址和电话号码(用逗号分隔),如下所示:
| user1 | email1@mail.com, email2@mail.com | +3612123123, +3623234234 |
这些表是:
user - stores the user's data
user_email - stores the user's email addresses
user_phone - stores the user's phone numbers
我尝试了一下:
SELECT user.id, user.name
(
SELECT array_agg(user_email.email)
FROM user_email
WHERE user_email.user_id = user.id
) AS EmailAddresses,
(
SELECT array_agg(user_phone.phone)
FROM user_phone
WHERE user_phone.user_id = user.id
) AS PhoneNumbers
FROM user
ORDER BY user.id
但这会导致荒谬的查询时间(34秒)。 比我尝试过的:
SELECT user.id, user.name, array_agg(user_email.email), array_agg(user_phone.phone)
FROM user
LEFT JOIN user_email ON user_email.user_id = user.id
LEFT JOIN user_phone ON user_phone.user_id = user.id
GROUP BY user.id
ORDER BY user.id
这将导致非常好的查询时间(大约100毫秒)。 但是这样可以列出电话号码和电子邮件地址的所有组合。 因此,如果我有3个电子邮件地址和3个电话号码,那么它将列出9个电子邮件地址(每个地址三倍)和9个电话号码。
有一种有效的方式来做我想要的吗?
DISTINCT
也可以在聚合表达式中使用:
SELECT "user".id, name, array_agg(DISTINCT email) emails, array_agg(DISTINCT phone) phones
FROM "user"
LEFT JOIN user_email ON user_email.user_id = "user".id
LEFT JOIN user_phone ON user_phone.user_id = "user".id
GROUP BY "user".id
ORDER BY "user".id;
注意:如果只需要逗号分隔的列表,则可能要使用string_agg()
而不是array_agg()
。
要么DISTINCT
SELECT DISTINCT user.id, user.name, array_agg(user_email.email), array_agg(user_phone.phone)
FROM user
LEFT JOIN user_email ON user_email.user_id = user.id
LEFT JOIN user_phone ON user_phone.user_id = user.id
GROUP BY user.id
ORDER BY user.id
或INNER
加盟
SELECT user.id, user.name, array_agg(user_email.email), array_agg(user_phone.phone)
FROM user
INNER JOIN user_email ON user_email.user_id = user.id
INNER JOIN user_phone ON user_phone.user_id = user.id
GROUP BY user.id
ORDER BY user.id
或两者
SELECT DISTINCT user.id, user.name, array_agg(user_email.email), array_agg(user_phone.phone)
FROM user
INNER JOIN user_email ON user_email.user_id = user.id
INNER JOIN user_phone ON user_phone.user_id = user.id
GROUP BY user.id
ORDER BY user.id
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