“Hey, what’s going on with my applications? I installed a newer version of MySQL. I have queries that perfectly run with the older version and now I have a lot of errors.”
This is a question some customers have asked me after upgrading MySQL. In this article, we’ll see what one of the most frequent causes of this issue is, and how to solve it.
We are talking about this error:
ERROR 1055 (42000): Expression #2 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'test.web_log.user_id' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by
Have you ever seen it?
SQL_MODE
As the first thing let me introduce the concept of SQL_MODE.
MySQL can work using different SQL modes that affect the syntax of the queries and validation checks. Based on the configured value of the …
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