[Spring] querydsl - 집합

집합 함수

@Test
public void aggregation() {
  List<Tuple> result = queryFactory
    .select(
      member.count(),
      member.age.sum(),
      member.age.avg(),
      member.age.max(),
      member.age.min()
    )
    .from(member)
    .fetch();

  Tuple tuple = result.get(0);
  assertThat(tuple.get(member.count())).isEqualTo(4);
  assertThat(tuple.get(member.age.sum())).isEqualTo(100);
  assertThat(tuple.get(member.age.avg())).isEqualTo(25);
  assertThat(tuple.get(member.age.max())).isEqualTo(40);
  assertThat(tuple.get(member.age.min())).isEqualTo(10);

}

- tuple로 반환해서 Q클래스로 get 가능

 

GroupBy 사용

/**
* 팀의 이름과 각 팀의 평균 연령을 구해라
*/
@Test
public void group() throws Exception{
  //given
  List<Tuple> result = queryFactory
    .select(team.name, member.age.avg())
    .from(member)
    .join(member.team, team)
    .groupBy(team.name)
    .fetch();

  Tuple teamA = result.get(0);
  Tuple teamB = result.get(1);

  assertThat(teamA.get(team.name)).isEqualTo("teamA");
  assertThat(teamA.get(member.age.avg())).isEqualTo(15);

  assertThat(teamB.get(team.name)).isEqualTo("teamB");
  assertThat(teamB.get(member.age.avg())).isEqualTo(35);

  //when

  //then

}

 

출처 : 스프링 핵심 원리 - 기본편 - 인프런 | 학습 페이지 (inflearn.com)