mysql - 宏扩展期间出现异常 : [error] java. lang.IllegalStateException:聚合组无效:

Question

我在 MYSQL 中有一个这样的表。

create table Employee(
 id tinyint,
 name char(36),
 is_permanent tinyint,
 company_name char(36),
 designation Char(36),
 primary key (id)

);

我想使用 Quill SQL 在此表上编写 SELECT 查询。

 select count(1),  sum((case when (`designation` = 'software') then 1 else 0 end)) from employee group by company_name;

我写了一个模型并且

case class Employee(id: Int,
                    name: String,
                    is_permanent: Boolean,
                    company_name: String,
                    designation: Designation)

  trait Designation {
   val value: String
  }

  case object SoftwareEngineer extends Designation {
     override val value: String = "software"
  }

 case object MechanicalEngineer extends Designation {
   override val value: String = "mechanical"
  }

我使用鹅毛笔的查询是

ctx.run {
  query[Employee].groupBy(_.company_name).map {
    case (compName, employeeTable) =>
      (employeeTable.size,
       employeeTable.filter(_.designation == lift(SoftwareEngineer)).size,
       compName)
  }
}

其中 ctx 是 quill 上下文。

但是编译器显示错误

exception during macro expansion: 
 [error] java.lang.IllegalStateException: Invalid group by aggregation: 'x48.filter(x49 => 
 x49.designation == ?).size'

group by 子句中过滤计数的计算方式是否正确？如果没有，还有其他方法吗？

Answer 1

查找 group by 子句的条件计数的方法不是

 employeeTable.filter(_.designation == lift(SoftwareEngineer)).size,

但是

 employeeTable.map { i =>
          if (i.`designation` == lift(SoftwareEngineer)) 1
          else 0
        }.sum

当然，为指定定义了适当的编码器