If your app was written for older versions of MySQL and is not compatible with strict SQL mode in MySQL 5.7, you can disable strict SQL mode. For example, apps such as WHMCS 6 and Craft 2 do not support strict SQL mode.
To disable strict SQL mode, SSH in to your server as root and create this file:
/etc/mysql/conf.d/disable_strict_mode.cnf
Open the file and enter these two lines:
[mysqld] sql_mode=IGNORE_SPACE,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
Restart MySQL with this command:
sudo service mysql restart
This change disables two SQL mode settings, STRICT_TRANS_TABLES and ONLY_FULL_GROUP_BY, that were added in MySQL 5.7 and cause problems for some older applications.
Confirming Strict SQL Mode Is Disabled
You can confirm strict SQL mode is disabled by running this command as root:
sudo mysql -i -BN -e 'SELECT @@sql_mode' | grep -E 'ONLY_FULL_GROUP_BY|STRICT_TRANS_TABLES'
If strict mode is disabled, you won't see any output from that command.
If disabling strict mode causes any problems for you, you can re-enable it by deleting that file and restarting MySQL again.
What Strict SQL Mode Errors Look Like
If your app isn't compatible with strict SQL mode, you'll often see SQL errors such as:
SQLSTATE[42000]: Syntax error or access violation: 1055 Expression #1 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'yourdbname.tblannouncements.date' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by
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