mySQL查询函数的语法错误,将小数等级转换为字母等级

Question

尝试在MySQL中创建函数以将小数等级转换为字母等级时,我遇到语法错误的麻烦.

可能是什么问题？

错误1064(42000):您的SQL语法有错误; 检查与mySQL服务器版本对应的手册,以便在'conv(gpa DOUBLE)RETURNS CHAR BEGIN
DECLARE grade CHAR 附近使用正确的语法;
在第1行选择gp'时的情况

这是我的代码:

delimiter $

CREATE FUNCTION conv(gpa DOUBLE) 
RETURNS CHAR
BEGIN 

DECLARE grade CHAR; 

SELECT CASE WHEN gpa BETWEEN 3.5 AND 4.0 THEN 'A' 
WHEN gpa BETWEEN 3.0 AND 3.4 THEN 'B' 
WHEN gpa BETWEEN 2.5 AND 2.9 THEN 'C' 
WHEN gpa BETWEEN 2.0 AND 2.4 THEN 'D' 
ELSE 'F' 
END INTO grade 

RETURN grade;

END $

Answer 1

您在末尾处缺少一个分号：

SELECT CASE WHEN gpa BETWEEN 3.5 AND 4.0 THEN 'A' 
WHEN gpa BETWEEN 3.0 AND 3.4 THEN 'B' 
WHEN gpa BETWEEN 2.5 AND 2.9 THEN 'C' 
WHEN gpa BETWEEN 2.0 AND 2.4 THEN 'D' 
ELSE 'F' 
END INTO grade;

另外，您可能不应该使用该名称，conv因为这已经意味着其他含义。