Question

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？它确实缺乏关于文档连接的信息。

更新1 我尝试了所有的组合，甚至像这样的

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，编译器会给我一个错误wrong number of parameters; expected = 2

所以我将sv.parameter_id替换为_.parameter_id，现在它争论加入它说：

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

我正在使用SLICK的最新版本，并且已弃用。我手动导入了

import scala.slick.lifted.Join现在它看起来像是常规的内部角色，因为它使用WHERE而不是在开启后使用。

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)

即使是这个也可以在ON部分添加条件

 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)

但这绝不会令人讨厌。

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

代替WHERE我需要AND。我应该用什么来提及这个条件，或者没有任何功能？

Answer 1

修改
OP在2个表对象的连接中寻找链接条件。

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)

<强> ORIGINAL
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) }

如何将AND添加到连接SLICK

1 个答案: