[QueryDSL] GroupBy

 

 

 

GroupBy

데이터를 그룹화하여 조회하기 위해 GroupBy를 사용합니다.

 

 

having을 통해 그룹화된 결과를 제한할 수 있습니다.

 

 

 

 

 

 

 

셋업 코드

@BeforeEach
fun before() {
    val teamA = Team(name = "teamA")
    val teamB = Team(name = "teamB")
    em.persist(teamA)
    em.persist(teamB)

    val members = listOf(
        Member(username = "member1", age = 10, team = teamA),
        Member(username = "member2", age = 20, team = teamA),
        Member(username = "member3", age = 30, team = teamB),
        Member(username = "member4", age = 40, team = teamB),
        Member(username = "member5", age = 50, team = teamA),
        Member(username = "member6", age = 60, team = teamA),
        Member(username = "member7", age = 70, team = teamB),
        Member(username = "member8", age = 80, team = teamB),
        Member(username = "member9", age = 90, team = teamA),
        Member(username = "member10", age = 100, team = teamA),
        Member(username = "member11", age = 110, team = teamB),
        Member(username = "member12", age = 120, team = teamB),
    )
    members.forEach { em.persist(it) }
    em.flush()
    em.clear()
}

 

 

 

 

사용

/**
 * 팀의 이름(select)과 각 팀의 평균 연령(select)
 */
@Test
fun testGroupBy() {
    //given
    val fetch = query
        .select(team.name, member.age.avg())
        .from(member)
        .join(member.team, team)
        .groupBy(team.name)
        .fetch()

    val teamA = fetch[0]
    val teamB = fetch[1]

    assertThat(teamA.get(team.name)).isEqualTo("teamA")
    assertThat(teamA.get(member.age.avg())).isEqualTo(55.0)
    assertThat(teamB.get(member.age.avg())).isEqualTo(75.0)
    assertThat(teamB.get(team.name)).isEqualTo("teamB")

}

 

 

 

 

 

 

 

having() 예시

...
.groupBy(team.name)
.having(member.age.loe(10))
...

 

 

 

 

 

 

 

Reference

실전! Querydsl - 인프런 | 강의