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mysql-如何创建自动递增的字符串？

2019-12-11 04:14:40 阅读：321 来源： 互联网

我面临用01、02,…,10、12递增字符串的问题

>我有一个SQL查询,该查询给了我AAAA06,这在我的数据库中最大.
>现在,我有一个要求,每当用户调用此命令时,它将使用最大编号检查数据库.当前为AAAA06(当前为最大值),应返回或打印AAAA07.
>同样,当最大值为AAAA09时,则应增加为AAAA10,依此类推
>作为一种语言,我正在使用Java,但是我想知道我可以通过自己的sql查询来实现此目的还是必须编写Java代码来实现此目的？

我正在使用的查询就像

select max(code) from mt_users where maincode='AAAA'

叫最大否是我做的.我只想增加或连接适合获得期望输出的任何内容.

它返回我AAAA06,因为这是当前的最大值.

重要事项

>最初为AAAA时,应显示AAAA01
>如果是AAAA09,则应显示AAAA10
>当它是AAAA99时将显示AAAA100

注意：当前我的最大身份为AAAA06,但是对于新用户而言,将来可能是AAAE,因此我必须以AAAE01开头.

解决方法:

简短答案-使用此查询：

SELECT id AS PrevID, CONCAT(
    SUBSTRING(id, 1, 4),
    IF(CAST(SUBSTRING(id, 5) AS UNSIGNED) <= 9, '0', ''),
    CAST(SUBSTRING(id, 5) AS UNSIGNED) + 1
) AS NextID
FROM (
    -- since you allow strings such as AAAA20 and AAAA100 you can no longer use MAX
    SELECT id
    FROM t
    ORDER BY SUBSTRING(id, 1, 4) DESC, CAST(SUBSTRING(id, 5) AS UNSIGNED) DESC
    LIMIT 1
) x

结果：

| PrevID  | NextID  | 
| AAAA100 | AAAA101 | 
| AAAA21  | AAAA22  | 
| AAAA06  | AAAA07  |

只是为了好玩,我写了这个存储过程,它生成的数字看起来像AAAA00 AAAA99 AAAB00等：

CREATE FUNCTION NextID(PrevID VARCHAR(6))
RETURNS VARCHAR(6)
BEGIN
    DECLARE s VARCHAR(4);
    DECLARE i INT;
    DECLARE j INT;

    SET s = LEFT(PrevID, 4);
    SET s = REPLACE(s, 'A', '0');
    SET s = REPLACE(s, 'B', '1');
    SET s = REPLACE(s, 'C', '2');
    SET s = REPLACE(s, 'D', '3');
    SET s = REPLACE(s, 'E', '4');
    SET s = REPLACE(s, 'F', '5');
    SET s = REPLACE(s, 'G', '6');
    SET s = REPLACE(s, 'H', '7');
    SET s = REPLACE(s, 'I', '8');
    SET s = REPLACE(s, 'J', '9');
    SET s = REPLACE(s, 'K', 'A');
    SET s = REPLACE(s, 'L', 'B');
    SET s = REPLACE(s, 'M', 'C');
    SET s = REPLACE(s, 'N', 'D');
    SET s = REPLACE(s, 'O', 'E');
    SET s = REPLACE(s, 'P', 'F');
    SET s = REPLACE(s, 'Q', 'G');
    SET s = REPLACE(s, 'R', 'H');
    SET s = REPLACE(s, 'S', 'I');
    SET s = REPLACE(s, 'T', 'J');
    SET s = REPLACE(s, 'U', 'K');
    SET s = REPLACE(s, 'V', 'L');
    SET s = REPLACE(s, 'W', 'M');
    SET s = REPLACE(s, 'X', 'N');
    SET s = REPLACE(s, 'Y', 'O');
    SET s = REPLACE(s, 'Z', 'P');

    SET i = RIGHT(PrevID, 2);
    SET j = CONV(s, 26, 10);

    SET i = i + 1;
    IF i > 99 THEN
        SET i = 0;
        SET j = j + 1;
    END IF;

    SET s = CONV(j, 10, 26);
    SET s = REPLACE(s, 'P', 'Z');
    SET s = REPLACE(s, 'O', 'Y');
    SET s = REPLACE(s, 'N', 'X');
    SET s = REPLACE(s, 'M', 'W');
    SET s = REPLACE(s, 'L', 'V');
    SET s = REPLACE(s, 'K', 'U');
    SET s = REPLACE(s, 'J', 'T');
    SET s = REPLACE(s, 'I', 'S');
    SET s = REPLACE(s, 'H', 'R');
    SET s = REPLACE(s, 'G', 'Q');
    SET s = REPLACE(s, 'F', 'P');
    SET s = REPLACE(s, 'E', 'O');
    SET s = REPLACE(s, 'D', 'N');
    SET s = REPLACE(s, 'C', 'M');
    SET s = REPLACE(s, 'B', 'L');
    SET s = REPLACE(s, 'A', 'K');
    SET s = REPLACE(s, '9', 'J');
    SET s = REPLACE(s, '8', 'I');
    SET s = REPLACE(s, '7', 'H');
    SET s = REPLACE(s, '6', 'G');
    SET s = REPLACE(s, '5', 'F');
    SET s = REPLACE(s, '4', 'E');
    SET s = REPLACE(s, '3', 'D');
    SET s = REPLACE(s, '2', 'C');
    SET s = REPLACE(s, '1', 'B');
    SET s = REPLACE(s, '0', 'A');

    RETURN CONCAT(LPAD(s, 4, 'A'), LPAD(i, 2, '0'));
END

SELECT NextID('AAAA01') -- AAAA02
SELECT NextID('AAAA99') -- AAAB00
SELECT NextID('AAAB99') -- AAAC00
SELECT NextID('AAAZ99') -- AABA00

标签：string,sql,mysql
来源： https://codeday.me/bug/20191211/2106457.html

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mysql-如何创建自动递增的字符串？