MySQL 简单函数不适用于变量声明

Question

我正在尝试在 phpMyAdmin 中的 MySQL 上定义我自己的 FUNCTION:

BEGIN
DECLARE output VARCHAR
DECLARE temp DATETIME
SET temp = DATEDIFF(NOW(), added)
CASE temp
WHEN 0 SET output = 'today'
WHEN 1 SET output = 'yesterday'
ELSE SET output = CONCAT(temp, ' days ago')
RETURN output
END

错误如下:

De volgende query is mislukt: "CREATE FUNCTION DAYSPASSED(date DATETIME) RETURNS VARCHAR(255) NOT DETERMINISTIC MODIFIES SQL DATA SQL SECURITY DEFINER BEGIN DECLARE output VARCHAR DECLARE temp DATETIME SET temp = DATEDIFF(NOW(), added) CASE temp WHEN 0 SET output = 'today' WHEN 1 SET output = 'yesterday' ELSE SET output = CONCAT(temp, ' days ago') RETURN output END"

MySQL retourneerde: #1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'DECLARE temp DATETIME SET temp = DATEDIFF(NOW(), added) CASE temp WHEN 0 SET ' at line 3

但是我不太明白它有什么问题。

Answer 1

您缺少一些分号，您的 varchar 的长度说明符，并且您的 case 语法中存在一些错误。这似乎适用于//定界符；

DELIMITER //
CREATE FUNCTION DAYSPASSED(added DATETIME) RETURNS VARCHAR(255) 
NOT DETERMINISTIC 
MODIFIES SQL DATA 
SQL SECURITY DEFINER 
BEGIN 
  DECLARE output VARCHAR(32);
  DECLARE temp INT;
  SET temp = DATEDIFF(NOW(), added);
  CASE temp WHEN 0 THEN SET output = 'today'; 
            WHEN 1 THEN SET output = 'yesterday';
            ELSE SET output = CONCAT(temp, ' days ago');
  END CASE;
  RETURN output;
END//
DELIMITER ;

An SQLfiddle to test with .