MySQL: Syntax error sql_mode=only_full_group_by

Understanding MySQL errors can be a daunting task, especially if you're new to the terrain. However, with a little patience and guidance, they can be deciphered and resolved. One common error that developers encounter is the mysql syntax error sql_mode=only_full_group_by. This error occurs when your SQL query doesn't follow the rules set by the MySQL ONLY_FULL_GROUP_BY mode. In this blog post, we will delve into three topics: understanding the ONLY_FULL_GROUP_BY mode, why the error occurs, and how to resolve it.

Understanding the 'ONLY_FULL_GROUP_BY' mode

The ONLY_FULL_GROUP_BY mode is a MySQL server mode that restricts the SELECT statements to only those with a grouping by clause. It means that every column in your SELECT list must be part of the GROUP BY clause unless it's an argument in an aggregate function like COUNT, SUM, AVG, etc. This mode is designed to ensure that the returned results are reliable and not ambiguous due to the grouping operation.

Why the 'mysql syntax error sql_mode=only_full_group_by' occurs

The mysql syntax error sql_mode=only_full_group_by error occurs when your SQL query violates the rules of the ONLY_FULL_GROUP_BY mode. Specifically, this error is triggered when you try to SELECT a column that isn't in your GROUP BY clause and isn't used with an aggregate function. For instance, when you're attempting to select columns that aren't part of the GROUP BY clause or aren't used as an argument with an aggregate function, MySQL throws this error to prevent ambiguous results.

How to resolve the 'mysql syntax error sql_mode=only_full_group_by'

Resolving the mysql syntax error sql_mode=only_full_group_by entails modifying either your SQL query or the SQL mode of your MySQL server. If you're sure that your query won't generate ambiguous results, you can disable the ONLY_FULL_GROUP_BY mode by setting the 'sql_mode' to an empty string or to any other modes except ONLY_FULL_GROUP_BY. Alternatively, you can adjust your query to comply with the ONLY_FULL_GROUP_BY rules - include all selected columns in your GROUP BY clause or use them as arguments in an aggregate function.

Remove ONLY_FULL_GROUP_BY from mysql console

mysql > SET GLOBAL sql_mode=(SELECT REPLACE(@@sql_mode,'ONLY_FULL_GROUP_BY',''));

Remember, this setting won't stay the same after restarting, then use:

mysql > SET PERSIST sql_mode=(SELECT REPLACE(@@sql_mode,'ONLY_FULL_GROUP_BY',''));


The mysql syntax error sql_mode=only_full_group_by might seem intimidating at first, but once you understand the ONLY_FULL_GROUP_BY mode and why the error occurs, it becomes much easier to tackle. Remember, you can either modify your SQL query to adhere to the ONLY_FULL_GROUP_BY rules or change your MySQL server mode to disable ONLY_FULL_GROUP_BY. Always ensure that your choice doesn't compromise the accuracy and reliability of your query results.

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