MySQL VARCHAR，如具有MIN和MAX字符长度的数据类型 [英] MySQL VARCHAR like Data type with MIN and MAX character lengths

问题描述

要查找与我想要的值类似的VARCHAR数据类型，但是有没有办法设置MIN/MAX字符长度?

Looking for a data type that is similar to VARCHAR as to the values I would like, but is there a way to have a MIN/MAX character length?

VARCHAR(6,10)

这将至少包含6个字符，最多10个字符.

This would have a minimum of 6 characters and a maximum of 10 characters.

推荐答案

您可以添加一个触发器，以在值超出范围时抛出异常，例如

You could add a trigger to throw an exception when the values are outside of the range, e.g.

DELIMITER $$

CREATE TRIGGER `insert_table_var` BEFORE INSERT ON `table` 
FOR EACH ROW
BEGIN
     DECLARE str_len INT DEFAULT 0;
     DECLARE max_len INT DEFAULT 10;
     DECLARE min_len INT DEFAULT 6;

     SET str_len = LENGTH(NEW.col);

     IF str_len > max_len OR str_len < min_len 
     THEN
           CALL col_length_outside_range_error();
     END IF;
END $$
DELIMITER ;;

虽然SIGNAL不可用，但调用未定义的存储过程就足够了(在本例中为col_length_outside_range_error).否则，我认为使用数据库的应用程序将需要进行检查.

Whilst SIGNAL is not available, calling an undefined stored procedure would suffice (in this case col_length_outside_range_error). Otherwise, I think that the application using the database is going to need to do the checks.

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