MyBatis自动生成Java/C#的Bean（Entity）的等价MYSQL实现函数

这是单元测试代码：TESTTITLECASE.sql

SELECT TITLECASE('ABC_DEF_hgk') as BEANNAME FROM DUAL;
SELECT TITLECASE('www_mysql_com') as BEANNAME FROM DUAL;
SELECT FIRSTLETTERUPPERCASE('ABC') FROM DUAL;
SELECT FIRSTLETTERUPPERCASE('aBC') FROM DUAL;
SELECT SUBSTRING_INDEX('www.mysql.com', '.', 2);
SELECT SUBSTRING_INDEX('www.mysql.com', '.', -2);
SELECT SUBSTRING_INDEX(SUBSTRING_INDEX('mysql', '.', 2), '.', -1);
SELECT SUBSTRING_INDEX(SUBSTRING_INDEX('www.mysql.com', '.', 1), '.', -1);
SELECT SUBSTRING_INDEX(SUBSTRING_INDEX('www.mysql.com', '.', 2), '.', -1);
SELECT SUBSTRING_INDEX(SUBSTRING_INDEX('www.mysql.com', '.', 3), '.', -1);

这是仿照MyBatis的功能实现：TITLECASE（这个是从Sublime里的Edit的Case下借鉴过来的）

CREATE DEFINER=`root`@`%` FUNCTION `TITLECASE`(x VARCHAR(255)) RETURNS varchar(255) CHARSET utf8
    READS SQL DATA
BEGIN
    DECLARE i INT;
    DECLARE n INT;
    DECLARE y VARCHAR(255);
    DECLARE word VARCHAR(255);
    DECLARE wordWithCase VARCHAR(255);

    SET i = 1;
    SET n = LENGTH(x) - LENGTH(REPLACE(x, '_', '')) + 1;
    SET y = '';

    WHILE i < n + 1 DO
        SET word = SUBSTRING_INDEX(SUBSTRING_INDEX(x, '_', i), '_' , -1);
        SET wordWithCase = CONCAT(IF(i=1,LOWER(SUBSTRING(word, 1, 1)),UPPER(SUBSTRING(word, 1, 1))), LOWER(SUBSTRING(word FROM 2)));
        SET y = CONCAT(y,wordWithCase);
        SET i = i + 1;
    END WHILE;

    RETURN y;
END

这是一个副产品：单词首字符大写：FIRSTLETTERUPPERCASE.sql

CREATE DEFINER=`root`@`%` FUNCTION `FIRSTLETTERUPPERCASE`(x VARCHAR(255)) RETURNS varchar(255) CHARSET utf8
    READS SQL DATA
BEGIN
    return CONCAT(UPPER(SUBSTRING(x, 1, 1)), LOWER(SUBSTRING(x FROM 2)));
END