QueryDsl SQL - 左连接子查询

Question

我正在使用 QueryDsl SQL 并且我想要 left join 一个子查询。这是纯SQL的查询

SELECT
  usr.memberId,
  payoutsBbf.totalPyts
FROM
  users usr
  LEFT JOIN
    (SELECT
       pyt.member_id   AS mmb_id,
       SUM(pyt.amount) AS totalPyts
  FROM
    payout pyt
  WHERE
    pyt.payoutPeriod < '2018-01-01'
    GROUP BY pyt.member_id) AS payoutsBbf ON usr.id = payoutsBbf.mmb_id

我希望将它写在QueryDsl SQL 中，并且将子查询留在主表users 中几乎很重要，因为这只是整个复杂查询的一个sn-p。

1. 我该如何处理LEFT JOIN x ON部分

2. SELECT payoutBbf.totalPyts部分中的子查询别名如何处理

Answer 1

我会这样做：

final StringPath payoutsBbf = stringPath("payoutsBbf");
final String mmbId = "mmb_id";
final String totalPyts = "totalPyts";
sqlQueryFactory.select(users.memberId, stringPath(payoutsBbf, totalPyts))
    .from(users).leftJoin(
        sqlQueryFactory.select(payout.member_id.as(mmbId), member_id.amount.sum().as(totalPyts))
            .from(payout).where(payout.payoutPeriod.lt("2018-01-01")).groupBy(payout.member_id),
        payoutsBbf
    ).on(users.id.eq(stringPath(payoutsBbf, mmbId))).fetch();

Answer 2

我认为这对你有用。不过这有点 hacky：

SQLQueryFactory sqlqf; // Should be @Autowired

QUsers qusers = new QUsers();
QPayouts qpayouts = new QPayouts();

Expression<Long> memberId = ExpressionUtils.as(qpayouts.memberId, "mmb_id");
Expression<Double> totalPayouts = ExpressionUtils.as(qpayouts.amount.sum(), "totalPayouts");

SQLQuery<Tuple> payoutsBbf = SQLExpressions.select(memberId, totalPayouts)
            .from(qpayouts)                
            .where(qpayouts.payoutPeriod.lt("2018-01-01")) // Use date object
            .groupBy(qpayouts.memberId);

final SimplePath<? extends SQLQuery> payoutsBBfPath = Expressions.path(payoutsBBfPath.getClass(), "payoutsBbf");

List<Tuple> fetch = sqlqf.select(
        qusers.memberId,                
        Expressions.path(payoutsBbf.getClass(), new PathMetadata(payoutsBBfPath, "totalPayouts", PathType.PROPERTY))
    )
    .from(qusers)
    .leftJoin(payoutsBbf, payoutsBBfPath)
    .addJoinFlag(" on payoutsBbf.mmb_id = users.id", JoinFlag.Position.BEFORE_CONDITION)
    .fetch();

注意使用 JoinFlag 来指定连接列，使用定义为payoutsBbf 的别名。还要注意使用Expressions.path() 来指定select() 部分中的子列