About the SQL injection of davwa, errors are reported: analysis and verification of the causes of legal mix of settlements for operation 'Union'

Project scenario ：

It's going on dvwa During range injection , I found that there were some bug：Illegal mix of collations for operation ‘UNION’

After query and verification , This problem is solved and analyzed .

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Cause analysis ：

The reason why this happens , yes union Of fields at both ends collatie（ Sort rule ） Different . namely dvwa Of first_name And last_name Character proofreading format and information_schema There was a conflict ：

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Solution ：

We need to dvwa Modify the proofing rules in , Let it information In the same , I'll change it to utf8_general_ci:

alter table users modify first_name varchar(15) character set utf8 collate utf8_general_ci

alter table users modify last_name varchar(15) character set utf8 collate utf8_general_ci

alter table users modify user varchar(15) character set utf8 collate utf8_general_ci


alter table users modify password varchar(15) character set utf8 collate utf8_general_ci

here , That's it ：