phoenix-framework - Ecto 模型 - 选择中的子查询

Question

我需要使用 Ecto 进行此 SQL 查询:

SELECT users.*, (select count(0) from money_transactions where from_id = users.id AND created_at > '2016-1-25 0:00:00.000000') as money_transactions_today_db FROM "users" WHERE "users"."client_token" = '123'

我尝试做这样的事情，但它不起作用:

query = from users in Like4uElixir.User,
        where: users.client_token in ^tokens,
        select: {users, (from money_transactions in Like4uElixir.MoneyTransaction,
                            where: money_transactions.from_id == users.id,
                            select: count(0))}

Ecto 是否支持子查询？如果没有，我该如何执行查询？

Answer 1

您可以使用查询片段:

query = from users in Like4uElixir.User,
        where: users.client_token in ^tokens,
        select: {users, (fragment("(SELECT COUNT(0) FROM money_transactions
                                    WHERE money_transactions.from_id == ?)", users.id))}

尽管在这种情况下，查询也可以使用常规连接和 group_by 编写。当前对 Ecto 中子查询的支持是有限的。