在MySQL的where子句中使用BLOB [英] Using BLOB in where clause in MySQL

问题描述

我正在开发一个应用程序，该应用程序需要通过检查存储在MySQL数据库中的指纹来对数据进行一些验证.建议使用诸如"AFIS"之类的专有软件.通过使用select语句的"where"子句中的BLOB列来过滤数据.这可能吗?

I am working on an application that will need to do some verification on data by checking fingerprints stored in a MySQL database.It was proposed to use proprietary software such as 'AFIS'..but i am wondering if the check can be done by using the BLOB column in the "where" clause of a select statement to filter the data. Is this possible?

我想到的代码是这样的:

The code i have in mind is something like this:

     Select id from mytable
     where image not in
    (select image from other table)

图像列为blob数据类型

With the image columns being of blob datatype

推荐答案

您的意思是这样的吗:

SELECT * FROM yourTable WHERE CHAR_LENGTH(your_blob_field) > 0

char_length()适用于Blob列类型...如果该值不是0，那么您知道里面有东西.

char_length() works on a blob column type... if that is anything but 0 then you know you've got something in there.

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