MySQL：使用嵌套 If 给出语法错误的存储过程的简单更新查询

Question

我正在创建一个 SQL 查询来创建一个存储过程来更新表的 Leaders_Score 和 Leaders_Icon 列，比如 chicago_public_schools。 我已经一次又一次地检查了语法，但无法弄清楚为什么会出现语法错误，任何人都可以告诉我这段代码中做错了什么：

   DELIMITER
    ;
CREATE PROCEDURE UPDATELEADERSSCORE(
    IN inSchoolID INTEGER,
    IN inLeaderScore INTEGER
) LANGUAGE SQL
BEGIN
    UPDATE
        chicago_public_schools
    SET
        Leaders_Score = inLeaderScore
    WHERE
        School_ID = inSchoolID; IF inLeaderScore > 80 AND inLeaderScore < 99 THEN
    UPDATE
        chicago_public_schools
    SET
        Leaders_Icon = 'Very Strong'
    WHERE
        School_ID = inSchoolID; ELSEIF inLeaderScore > 60 AND inLeaderScore < 79 THEN
    UPDATE
        chicago_public_schools
    SET
        Leaders_Icon = 'Strong'
    WHERE
        School_ID = inSchoolID; ELSEIF inLeaderScore > 40 AND inLeaderScore < 59 THEN
    UPDATE
        chicago_public_schools
    SET
        Leaders_Icon = 'Average'
    WHERE
        School_ID = inSchoolID; ELSEIF inLeaderScore > 20 AND inLeaderScore < 39 THEN
    UPDATE
        chicago_public_schools
    SET
        Leaders_Icon = 'Weak'
    WHERE
        School_ID = inSchoolID; ELSEIF inLeaderScore > 0 AND inLeaderScore < 19 THEN
    UPDATE
        chicago_public_schools
    SET
        Leaders_Icon = 'Very weak'
    WHERE
        School_ID = inSchoolID; ENDIF;
END;
DELIMITER
    ;

这是错误：

CREATE PROCEDURE UPDATELEADERSSCORE(
    IN inSchoolID INTEGER,
    IN inLeaderScore INTEGER
) LANGUAGE SQL
BEGIN
    UPDATE
        chicago_public_schools
    SET
        Leaders_Score = inLeaderScore
    WHERE
        School_ID = inSchoolID
MySQL said: Documentation

#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 '' at line 11

问候，T

Answer 1

看起来您正在尝试设置值，然后是基于该值的类别。 使用 CASE 语句会更清晰，例如：

UPDATE chicago_public_schools
SET
    Leaders_Score = inLeaderScore,
    Leaders_Icon = CASE WHEN inLeaderScore > 80 THEN 'Very Strong'
                        WHEN inLeaderScore > 60 THEN 'Strong'
                        WHEN inLeaderScore > 40 THEN 'Average'
                        WHEN inLeaderScore > 20 THEN 'Weak'
                        WHEN inLeaderScore > 0 THEN 'Very Weak'
                    END
WHERE
    School_ID = inSchoolID; 

Answer 2

我看到几个问题。

DELIMITER必须在同一行设置分隔符。 您不能在分隔符前添加换行符。

错误的：

DELIMITER
 ;

正确的：

DELIMITER ;

接下来，将 DELIMITER 设置为; 在编写包含的存储例程之前; 例程主体中的语句终止符。 您需要将定界符定义为不同于默认语句终止符的内容，因此例程主体中的分号不会终止整个 CREATE PROCEDURE 语句。 我认为您需要重新阅读https://dev.mysql.com/doc/refman/8.0/en/stored-programs-defining.html

最后， IF复合语句的结尾是END IF; , 不是ENDIF; . 参见https://dev.mysql.com/doc/refman/8.0/en/if.html