如何在MySQL上生成具有唯一字符序列的触发器？

o/

我想生成一个4个字符的序列，使用大小写+数字。。但是我想在MySQL数据库上插入新用户之前，使用触发器生成这个序列

类似于=“Ae5f”或“5Bd2”的内容

我正在使用

  CHAR( FLOOR(65 + (RAND() * 25))),
  CHAR( FLOOR(65 + (RAND() * 25))),
  CHAR( FLOOR(65 + (RAND() * 25))),
  CHAR( FLOOR(65 + (RAND() * 25)))

因此，代码将只生成4位大写字母，而不是唯一的值，有时会返回“重复条目”

有人能帮我吗

-----------------------编辑-----------------------

我在Base32中的最后一个实现

CREATE DEFINER=`root`@`localhost` TRIGGER `healthcare`.`TESTE_BEFORE_INSERT` BEFORE INSERT ON `teste` FOR EACH ROW
BEGIN
    DECLARE last_id integer;
    SET last_id = (SELECT MAX(ID) AS lastID FROM `healthcare`.`teste`);
    IF last_id IS NULL THEN
        SET last_id = 0;
    END IF;
    SET NEW.USER_KEY = conv((1048575-last_id), 10, 32); /* 1048575 = VVVV */
END

---

随机化解决方案将受到欢迎。

这是一个你可能会感兴趣的程序。其概念是为各种序列（在系统范围内使用）提供一个控制表。简言之，以下是一个卑鄙的人。它使用MySQL“意向锁”

您需要的是

Base36

数字功能，这就提供了其中的一部分。如何将其嵌入到设置中，如果您这样做，则取决于您

控制表：

-- drop table if exists sequences;
create table sequences
(   -- the numbers in here are the next numbers free to use
    -- so it is yours once you acquire the INTENTION lock
    -- but do an UPDATE for the next guy by incrementing the number
    -- and COMMIT
    id int auto_increment primary key,
    sectionType varchar(200) not null,
    nextSequence int not null,
    unique key(sectionType) -- perhaps overkill on index but meh
);

-- truncate table sequences;
insert sequences (sectionType,nextSequence) values
('Chassis Serial Number',1),('Engine Block Serial Number',1),('base36number',0);

存储过程：

DROP PROCEDURE IF EXISTS getBase36;
DELIMITER $$CREATE PROCEDURE getBase36
(   OUT sOutVar CHAR(4) -- out parameter for base36 number
)
BEGIN
    DECLARE num_to_use INT;
    DECLARE i1,i2 INT;
    DECLARE sSendBack CHAR(4);

    -- 0-9 is ascii 48 to 57
    -- A-Z is ascii 65 to 90
    -- 0000 to ZZZZ in that order. 0 to 9 then A etc 36 positions
    -- first char is 0. 36th char is Z. Base36,  0 is 0000 , 35 is 000Z, 36 is 00010
    -- 1.68M possibilities
    -- output ranges from 0000 to ZZZZ
    START TRANSACTION;
    SELECT nextSequence into num_to_use from sequences where sectionType='base36number' FOR UPDATE;
    UPDATE sequences set nextSequence=nextSequence+1 where sectionType='base36number';
    COMMIT; -- because of this, it cannot be a FUNCTION but must be a stored proc, else error 1422
            -- which is Error 1422: Explicit or implicit commit is not allowed in a stored function or trigger

    SET sOutVar='';

    -- IF num_to_use>1679616 THEN
    --  SET sSendBack='----'; 
    --     -- SET sOutVar='----'; -- ran out of space. Think up something else. This was your idea, afterall :p
    --  -- we will drop out of routine
    -- END IF;

    IF num_to_use<1679616 THEN
        -- I don't feel like doing a LOOP for the below
        -- Honestly just because I am tired at the moment.

        SET i2=num_to_use;
        SET i1=FLOOR(i2/46656); -- 46656 is 36 cubed
        IF i1 between 0 and 9 THEN
            SET sSendBack=CHAR(48+i1);
        ELSE
            SET sSendBack=CHAR(65+i1-10);
        END IF;

        SET i2=i2-(i1*46656); 
        SET i1=FLOOR(i2/1296); -- 1296 is 36 squared
        IF i1 between 0 and 9 THEN
            SET sSendBack=CONCAT(sSendBack,CHAR(48+i1));
        ELSE
            SET sSendBack=CONCAT(sSendBack,CHAR(65+i1-10));
        END IF;

        SET i2=i2-(i1*1296); 
        SET i1=FLOOR(i2/36); -- 36 is 36 to the first power
        IF i1 between 0 and 9 THEN
            SET sSendBack=CONCAT(sSendBack,CHAR(48+i1));
        ELSE
            SET sSendBack=CONCAT(sSendBack,CHAR(65+i1-10));
        END IF;

        SET i2=i2-(i1*36);
        SET i1=FLOOR(i2/1); -- 1 is 36 to the 0th
        IF i1 between 0 and 9 THEN
            SET sSendBack=CONCAT(sSendBack,CHAR(48+i1));
        ELSE
            SET sSendBack=CONCAT(sSendBack,CHAR(65+i1-10));
        END IF;
        SET sOutVar=sSendBack; -- base36 number (a string) to OUT parameter
        SELECT num_to_use,sOutVar as yourNumber; -- send out as a resultset too
    ELSE
        SET sSendBack='----';
        SET sOutVar=sSendBack;  -- base36 number (a string) to OUT parameter
        select num_to_use,sOutVar as yourNumber; -- send out as a resultset too
    END IF;
END;$$
DELIMITER ;  

---

这里有一个你可能会感兴趣的例行公事。其概念是为各种序列（在系统范围内使用）提供一个控制表。简言之，以下是一个卑鄙的人。它使用MySQL“意向锁”

您需要的是

Base36

数字功能，这就提供了其中的一部分。如何将其嵌入到设置中，如果您这样做，则取决于您

控制表：

-- drop table if exists sequences;
create table sequences
(   -- the numbers in here are the next numbers free to use
    -- so it is yours once you acquire the INTENTION lock
    -- but do an UPDATE for the next guy by incrementing the number
    -- and COMMIT
    id int auto_increment primary key,
    sectionType varchar(200) not null,
    nextSequence int not null,
    unique key(sectionType) -- perhaps overkill on index but meh
);

-- truncate table sequences;
insert sequences (sectionType,nextSequence) values
('Chassis Serial Number',1),('Engine Block Serial Number',1),('base36number',0);

存储过程：

DROP PROCEDURE IF EXISTS getBase36;
DELIMITER $$CREATE PROCEDURE getBase36
(   OUT sOutVar CHAR(4) -- out parameter for base36 number
)
BEGIN
    DECLARE num_to_use INT;
    DECLARE i1,i2 INT;
    DECLARE sSendBack CHAR(4);

    -- 0-9 is ascii 48 to 57
    -- A-Z is ascii 65 to 90
    -- 0000 to ZZZZ in that order. 0 to 9 then A etc 36 positions
    -- first char is 0. 36th char is Z. Base36,  0 is 0000 , 35 is 000Z, 36 is 00010
    -- 1.68M possibilities
    -- output ranges from 0000 to ZZZZ
    START TRANSACTION;
    SELECT nextSequence into num_to_use from sequences where sectionType='base36number' FOR UPDATE;
    UPDATE sequences set nextSequence=nextSequence+1 where sectionType='base36number';
    COMMIT; -- because of this, it cannot be a FUNCTION but must be a stored proc, else error 1422
            -- which is Error 1422: Explicit or implicit commit is not allowed in a stored function or trigger

    SET sOutVar='';

    -- IF num_to_use>1679616 THEN
    --  SET sSendBack='----'; 
    --     -- SET sOutVar='----'; -- ran out of space. Think up something else. This was your idea, afterall :p
    --  -- we will drop out of routine
    -- END IF;

    IF num_to_use<1679616 THEN
        -- I don't feel like doing a LOOP for the below
        -- Honestly just because I am tired at the moment.

        SET i2=num_to_use;
        SET i1=FLOOR(i2/46656); -- 46656 is 36 cubed
        IF i1 between 0 and 9 THEN
            SET sSendBack=CHAR(48+i1);
        ELSE
            SET sSendBack=CHAR(65+i1-10);
        END IF;

        SET i2=i2-(i1*46656); 
        SET i1=FLOOR(i2/1296); -- 1296 is 36 squared
        IF i1 between 0 and 9 THEN
            SET sSendBack=CONCAT(sSendBack,CHAR(48+i1));
        ELSE
            SET sSendBack=CONCAT(sSendBack,CHAR(65+i1-10));
        END IF;

        SET i2=i2-(i1*1296); 
        SET i1=FLOOR(i2/36); -- 36 is 36 to the first power
        IF i1 between 0 and 9 THEN
            SET sSendBack=CONCAT(sSendBack,CHAR(48+i1));
        ELSE
            SET sSendBack=CONCAT(sSendBack,CHAR(65+i1-10));
        END IF;

        SET i2=i2-(i1*36);
        SET i1=FLOOR(i2/1); -- 1 is 36 to the 0th
        IF i1 between 0 and 9 THEN
            SET sSendBack=CONCAT(sSendBack,CHAR(48+i1));
        ELSE
            SET sSendBack=CONCAT(sSendBack,CHAR(65+i1-10));
        END IF;
        SET sOutVar=sSendBack; -- base36 number (a string) to OUT parameter
        SELECT num_to_use,sOutVar as yourNumber; -- send out as a resultset too
    ELSE
        SET sSendBack='----';
        SET sOutVar=sSendBack;  -- base36 number (a string) to OUT parameter
        select num_to_use,sOutVar as yourNumber; -- send out as a resultset too
    END IF;
END;$$
DELIMITER ;  

---

如果你需要它是唯一的，我不会让它是随机的，特别是只有4个字符。我只需要一个普通的序列，你可以将它转换成基数36，比如（你可以把基数62的小写字母加进去）。我不确定是否可以从MySQL中的触发器调用函数。是否需要大小写字母？让代码只由数字和大写字母组成行吗？我需要生成一个具有一定可伸缩性的小“散列”以供一千或一百万用户使用（如果可能的话..只是为了不需要进行将来的维护）。。但是会被老年用户使用，所以我想做一些尽可能小的东西。Base32可能就足够了：1.048.575=vvv~so。。如何授予哈希唯一性*我想进行（1048575-USER_ID）转换，但会为初始用户生成最简单的ID，如“VVVE”、“VVUA”。。有什么想法可以随机化并成为唯一的值吗？如果你需要它是唯一的，我不会让它是随机的，特别是只有4个字符。我只需要一个普通的序列，你可以将它转换成基数36，比如（你可以把基数62的小写字母加进去）。我不确定是否可以从MySQL中的触发器调用函数。是否需要大小写字母？让代码只由数字和大写字母组成行吗？我需要生成一个具有一定可伸缩性的小“散列”以供一千或一百万用户使用（如果可能的话..只是为了不需要进行将来的维护）。。但是会被老年用户使用，所以我想做一些尽可能小的东西。Base32可能就足够了：1.048.575=vvv~so。。如何授予哈希唯一性*我想进行（1048575-USER_ID）转换，但会为初始用户生成最简单的ID，如“VVVE”、“VVUA”。。是否有随机化和唯一化的想法？