Nối chuỗi (CONCAT) cột trong SELECT MySQL?

Sử dụng CONCAT(cot, 'chuoi_them') trực tiếp trong danh sách cột SELECT.

Cú pháp:

SELECT CONCAT(cot1, 'chuoi_1'), CONCAT(cot2, 'chuoi_2'), ... FROM ten_bang;

Ví dụ:

CREATE TABLE selectConcat (StudentId INT, StudentName VARCHAR(100), StudentAge INT);
INSERT INTO selectConcat VALUES
(1,'Carol',23), (2,'John',24), (3,'Adam',25), (4,'Bob',21), (5,'Sam',22);

Nối chuỗi mô tả:

SELECT CONCAT(StudentId, ' as an Id'), CONCAT(StudentName, ' as a Name') FROM selectConcat;

Kết quả

+-------------------------------+----------------------------------+
| concat(StudentId,' as an Id') | concat(StudentName,' as a Name') |
+-------------------------------+----------------------------------+
| 1 as an Id                    | Carol as a Name                  |
| 2 as an Id                    | John as a Name                   |
| 3 as an Id                    | Adam as a Name                   |
| 4 as an Id                    | Bob as a Name                    |
| 5 as an Id                    | Sam as a Name                    |
+-------------------------------+----------------------------------+

Mẹo: Dùng alias cho cột kết quả: CONCAT(StudentId, ' as an Id') AS IdDesc. Dùng CONCAT_WS nếu có thể NULL.