确定mysql中的一列中允许的最大长度 [英] Determine max length allowed in a column in mysql

问题描述

表的结构类似于:

registrant_id   varchar(16)
registrant_name     varchar(128)

我想运行一个查询，该查询显示所有与最大PERMISSIBLE长度相匹配的条目，即我目前为上述操作所做的事情:

I want to run a query that displays all those entries which match the maximum PERMISSIBLE length, ie what I do currently do for the above:

SELECT *
FROM `tm_registrant`
WHERE length( `registrant_name` ) = 128

但是，我不想对128进行硬编码，因为我有很多列，并且想运行一个查询来查看所有至少有一个完全填满"的列的条目.

However, I dont want to hardcode 128 as I have many columns and want to run one query to see all the entries which have atleast one completely 'filled up' column.

推荐答案

SELECT CHARACTER_MAXIMUM_LENGTH
  FROM INFORMATION_SCHEMA.COLUMNS
 WHERE table_name = 'your_table_name'
   AND table_schema = 'your_db_name'
   AND column_name = 'your_column_name'
 LIMIT 0 , 1

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