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我在 SLICK 中编写查询时遇到问题这是我对 MySql 数据库的请求：

SELECT * FROM readings AS r
JOIN parameters AS p
LEFT JOIN sensorvalues AS sv ON sv.parameter_id=p.id AND sv.reading_id=r.id

如何使用 SLICK 编写它？确实缺乏有关文档中连接的信息。

更新 1 我尝试了所有组合，即使是这样的组合

val q = for{
  Join(p,sv) <- Parameters leftJoin SensorValues on (_.id is sv.parameter_id)
  r <- Readings if sv.reading_id is r.id
} yield(r,p,sv)

在这种情况下，编译器给了我一个错误wrong number of parameters; expected = 2

所以我将 sv.parameter_id 替换为 _.parameter_id 现在它争论 Join 它说：

constructor cannot be instantiated to expected type; found : models.Join required: (models.Parameters.type, models.SensorValues.type)

我正在使用最新版本的 SLICK，但已弃用。我手动导入

import scala.slick.lifted.Join现在它看起来像是常规的 innerJoin，因为它使用 WHERE 而不是在 ON 之后放置和。

SQL 生成的购买查询：

select x2.id, x2.platform_id, x2.date, x3.x4, x3.x5, x3.x6, x7.x8, x7.x9, x7.x10, x7.x11 from (select x12.id as x4, x12.name as x5, x12.units as x6 from parameters x12) x3 left outer join (select x13.id as x8, x13.reading_id as x9, x13.parameter_id as x10, x13.value as x11 from sensorValues x13) x7 on x3.x4 = x7.x10, readings x2 where true and (x7.x9 = x2.id)

即使是在 ON 部分添加条件的情况下也会很好

 val readings = for {
        all <-Readings join Parameters leftJoin SensorValues on (_._2.id is _.parameter_id) if(all._1._1.id === all._2.reading_id)
      } yield (all._1._1,all._1._2,all._2)

但这从未发生过。

SELECT
    x2.x3,
    x2.x4,
    x2.x5,
    x2.x6,
    x2.x7,
    x2.x8,
    x9.x10,
    x9.x11,
    x9.x12,
    x9.x13
FROM
    (
        SELECT
            x14.x15 AS x3,
            x14.x16 AS x4,
            x14.x17 AS x5,
            x18.x19 AS x6,
            x18.x20 AS x7,
            x18.x21 AS x8
        FROM
            (
                SELECT
                    x22.`id` AS x15,
                    x22.`platform_id` AS x16,
                    x22.`date` AS x17
                FROM
                    `readings` x22
            )x14
        INNER JOIN(
            SELECT
                x23.`id` AS x19,
                x23.`name` AS x20,
                x23.`units` AS x21
            FROM
                `parameters` x23
        )x18
    )x2
LEFT OUTER JOIN(
    SELECT
        x24.`id` AS x10,
        x24.`reading_id` AS x11,
        x24.`parameter_id` AS x12,
        x24.`value` AS x13
    FROM
        `sensorValues` x24
)x9 ON x2.x6 = x9.x12
WHERE
    x2.x3 = x9.x11

相反WHERE，我需要AND. 我应该用什么来提及这种情况，或者 slick 中没有任何功能？

4

1 回答 1

5

编辑
OP 正在寻找2 个表对象连接中的条件链。

这应该编译： 

val q = for{
  r <- Readings
  Join(p,s) <- Params leftJoin Sensors on (
    (a,b)=> (a.id is b.parameter_id) && (b.reading_id is r.id)
  )
} yield(r,p,s)

原创
尝试这样的事情：

val q = for{
  Join(p,s) <- Params leftJoin Sensors on (_.id is s.parameter_id)
  r <- Readings if s.reading_id is r.id
} yield(r,p,s)

val result = 
  q.list.map{ case(r,p,s)=>
    SomeCaseClass(r,p,s)
  }
于 2012-11-15T23:31:10.727 回答