Cách lấy độ dài VarChar lớn nhất trong MySQL

Để lấy độ dài varchar lớn nhất, sử dụng hàm CHAR_LENGTH().

Cú pháp:

SELECT MAX(CHAR_LENGTH(yourColumnName)) AS anyAliasName FROM yourTableName;

Tạo bảng minh họa:

mysql> CREATE TABLE CharLengthDemo (
    -> Id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    -> Sentence VARCHAR(255)
    -> );

Chèn dữ liệu:

mysql> INSERT INTO CharLengthDemo(Sentence) VALUES('Java is an object oriented programming language');
mysql> INSERT INTO CharLengthDemo(Sentence) VALUES('MySQL is a Relational Database Management System');
mysql> INSERT INTO CharLengthDemo(Sentence) VALUES('JSP uses Java Programming Language');
mysql> INSERT INTO CharLengthDemo(Sentence) VALUES('Object is a root class in java');

Hiển thị dữ liệu:

mysql> SELECT * FROM CharLengthDemo;

Kết quả:

+----+--------------------------------------------------+
| Id | Sentence                                         |
+----+--------------------------------------------------+
|  1 | Java is an object oriented programming language  |
|  2 | MySQL is a Relational Database Management System |
|  3 | JSP uses Java Programming Language               |
|  4 | Object is a root class in java                   |
+----+--------------------------------------------------+

Truy vấn lấy độ dài lớn nhất:

mysql> SELECT MAX(CHAR_LENGTH(Sentence)) AS MAXLENGTH FROM CharLengthDemo;

Kết quả:

+-----------+
| MAXLENGTH |
+-----------+
|        48 |
+-----------+