char函数sql mysql_mysql sql LENGTH,RIGHT,CHAR_LENGTH字符处理函数

mysql教程 sql LENGTH,RIGHT,CHAR_LENGTH字符处理函数

LENGTH(str)

OCTET_LENGTH(str)

CHAR_LENGTH(str)

CHARACTER_LENGTH(str)

返回字符串str的长度。

mysql> select LENGTH('text');

-> 4

mysql> select OCTET_LENGTH('text');

-> 4

mysql> SELECT

->    CONCAT(RIGHT(Name, LENGTH(Name) - INSTR(Name, ' ') + 1),

->           ', ', LEFT(Name, INSTR(Name, ' ') - 1))

->    AS StudentName

-> FROM Student

-> ORDER BY StudentName;

+---------------+

| StudentName   |

+---------------+

|  But, Cory    |

|  Harvests, JJ |

|  Wang, Joe    |

+---------------+

3 rows in set (0.04 sec)

*/

RIGHT(str,len)

返回字符串str的最右面len个字符。

mysql> select RIGHT('foobarbar', 4);

-> 'rbar'

该函数是多字节可靠的

/* Prepare the data */

DROP TABLE Student;

CREATE TABLE Student (

StudentID INT NOT NULL PRIMARY KEY,

Name      VARCHAR(50) NOT NULL

)TYPE = InnoDB;

/* Insert data for testing */

INSERT INTO Student (StudentID,Name) VALUES (1,'Joe Wang');

INSERT INTO Student (StudentID,Name) VALUES (2,'Cory But');

INSERT INTO Student (StudentID,Name) VALUES (3,'JJ Harvests');

Select * from StudentExam;

/* Real command */

SELECT

CONCAT(RIGHT(Name, LENGTH(Name) - INSTR(Name, ' ') + 1),

', ', LEFT(Name, INSTR(Name, ' ') - 1))

AS StudentName

FROM Student

ORDER BY StudentName;

注意，对于多字节字符，其CHAR_LENGTH()仅计算一次。

SELECT Name, CHAR_LENGTH(Name) AS CharLength

FROM DVDs

WHERE CHAR_LENGTH(Name)>5

ORDER BY Name;