concatenate : Combine Data For Cleaner Output
CONCAT(column, 'text', anotherColumn, 'more text')
예시
SELECT
CONCAT(author_fname, ' ', author_lname)
FROM books;
**CONCAT_WS: Concatenate With Seperator
예시: 구분자 ' - '를 사이에 넣어 데이터 결합하기
SELECT
CONCAT_WS(' - ', title, author_fname, author_lname)
FROM books;
**SUBSTRING() = SUBSTR()
예시: 'Hello World' 의 1번째부터 4번째 캐릭터 출력하기
SELECT SUBSTRING('Hello World', 1, 4);
+--------------------------------+
| SUBSTRING('Hello World', 1, 4) |
+--------------------------------+
| Hell |
+--------------------------------+
예시: 'Hello World' 의 7번째 부터 끝까지 출력하기
SELECT SUBSTRING('Hello World', 7);
+-----------------------------+
| SUBSTRING('Hello World', 7) |
+-----------------------------+
| World |
+-----------------------------+
예시: 'Hello World' 의 뒤에서 3번째부터 끝까지 출력
SELECT SUBSTRING('Hello World', -3);
+------------------------------+
| SUBSTRING('Hello World', -3) |
+------------------------------+
| rld |
+------------------------------+
예시:
SELECT
REPLACE('cheese bread coffee milk', ' ', ' and ');
+---------------------------------------------------+
| REPLACE('cheese bread coffee milk', ' ', ' and ') |
+---------------------------------------------------+
| cheese and bread and coffee and milk |
+---------------------------------------------------+
SELECT REVERSE('Hello World');
+------------------------+
| REVERSE('Hello World') |
+------------------------+
| dlroW olleH |
+------------------------+
Counts Characters in String
SELECT CHAR_LENGTH('Hello World');
+----------------------------+
| CHAR_LENGTH('Hello World') |
+----------------------------+
| 11 |
+----------------------------+
change a string's case
SELECT UPPER('Hello World');
+----------------------+
| UPPER('Hello World') |
+----------------------+
| HELLO WORLD |
+----------------------+
SELECT LOWER('Hello World');
+----------------------+
| LOWER('Hello World') |
+----------------------+
| hello world |
+----------------------+