mysql 문자열 결합 : concat() 함수

CONCAT()
함수는 두 개 이상의 문자열을 결합(연결)하여 단일 문자열을 만드는 데 사용됩니다. 하나 이상의 문자열 인수를 사용하고 이를 결합하여 새 문자열을 반환합니다. 인수 수는 다양할 수 있으며 문자열, 열 또는 둘을 혼합하여 연결할 수 있습니다.

기본형식

CONCAT(string1, string2, ...)

SELECT concat('my','zzz','sql')

 

 

-- 홍길동(S00001) <<- 이런 형식으로 사원명 출력

SELECT concat(emp_name,'(',emp_id,')') AS emp_name FROM employee WHERE emp_name = '홍길동'

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추가예시

 

 

CONCAT()다음은 SQL에서 함수를 사용하는 방법에 대한 몇 가지 예입니다 .

두 문자열 연결:

SELECT CONCAT('Hello', 'World') AS ConcatenatedString;
-- Output: "HelloWorld"

문자열을 열 값과 연결:

SELECT CONCAT('Name: ', first_name, ' ', last_name) AS Full_Name
FROM employees;
-- Output: "Name: John Doe"

여러 열 연결:

 SELECT CONCAT(first_name, ' ', last_name) AS Full_Name
FROM employees;
-- Output: "John Doe"

열과 리터럴 문자열 연결:

SELECT CONCAT('User ID: ', user_id, ', Name: ', full_name) AS UserInfo
FROM users;
-- Output: "User ID: 123, Name: Alice Johnson"

NULL 값과 연결:

SELECT CONCAT('Hello', NULL, 'World') AS ConcatenatedString;
-- Output: "HelloWorld" (NULL values are treated as empty strings)

두 개 이상의 문자열 연결:

SELECT CONCAT('This', ' is', ' a', ' concatenated', ' sentence.') AS Result;
-- Output: "This is a concatenated sentence."

CONCAT()WHERE 절에서 사용 :

SELECT full_name
FROM employees
WHERE CONCAT(first_name, ' ', last_name) = 'John Doe';