How to Fix MySQL Error #1055: \'Expression of SELECT list is not in GROUP BY clause\'?

#1055 - Expression of SELECT list is not in GROUP BY clause and contains nonaggregated column this is incompatible with sql_mode=only_full_group_by

In this programming issue, the user encounters the error message "#1055 - Expression of SELECT list is not in GROUP BY clause and contains nonaggregated column this is incompatible with sql_mode=only_full_group_by" while attempting to run a query in MySQL. To resolve this error, the user must modify the MySQL configuration file (mysql.cnf) to set the sql_mode parameter to STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION.

The user provides the following steps to successfully resolve the error:

1. Edit the MySQL configuration file (/etc/mysql/conf.d/mysql.cnf) using a text editor like vim:

sudo vim /etc/mysql/conf.d/mysql.cnf

2. Scroll to the bottom of the file and add the following lines:

[mysqld]
sql_mode=STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION

3. Save the file and exit the text editor.
4. Restart the MySQL service:

sudo service mysql restart

After completing these steps, the user should be able to execute the original query without encountering the error.

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