상수, 문자 더하기

1. 상수 

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• selcrt 안에
• Expressions.constant("~~")

    @Test
    public void constant(){
        List<Tuple> result = queryFactory
                .select(member.username, Expressions.constant("A"))
                .from(member)
                .fetch();
        for (Tuple tuple : result) {
            System.out.println("tuple = " + tuple);
        }
    }

tuple = [member1, A]
tuple = [member2, A]
tuple = [member3, A]
tuple = [member4, A]

 

2. 문자 더하기

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• conacat 사용
• ~.stringValue()
• 문자가 아닌 다른 타입들은 stringValue() 로
  문자로 변환할 수 있다. 이 방법은 ENUM을 처리할 때도 자주 사용한다.

    @Test
    public void concat(){
        //{user_name}_{age}
        List<String> result = queryFactory
                .select(member.username.concat("_").concat(member.age.stringValue()))
                .from(member)
                .where(member.username.eq("member1"))
                .fetch();
        for (String s : result) {
            System.out.println("s = " + s);
        }
    
    }

s = member1_10

 

4. GitHub : 210903 Constant, concat

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GitHub - bsh6463/Querydsl