MySQL not writing to database

Hello,

I would recommend making sure that you’ve granted all privileges to the new user that you’ve created:

GRANT ALL ON example_database.* TO 'example_user'@'%';

If this still does not help, can you share an example of the problematic code snippet that you are using the insert data into the database?

Regards, Bobby

Here are the usual stuff to check when in such situations

The issue you’re describing—successful reads but failed writes to the database—indicates a deeper issue that may not be directly related to MySQL permissions. Here’s a step-by-step guide to diagnose and resolve the issue:

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1. Check MySQL User Permissions

Even though you’ve already given full privileges to the user, confirm it explicitly using the following commands:

SHOW GRANTS FOR 'your_user'@'localhost';

Ensure you see something like:

GRANT ALL PRIVILEGES ON your_database.* TO 'your_user'@'localhost';

If you don’t see the necessary privileges, reapply them:

GRANT ALL PRIVILEGES ON your_database.* TO 'your_user'@'localhost';
FLUSH PRIVILEGES;

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2. Verify SQL Mode

Certain SQL modes can prevent writes, such as STRICT_TRANS_TABLES. Check the current SQL mode:

SHOW VARIABLES LIKE 'sql_mode';

If STRICT_TRANS_TABLES or similar is set, it may reject writes that violate schema constraints. You can modify it temporarily for testing:

SET GLOBAL sql_mode = '';

To make it permanent, edit /etc/mysql/my.cnf or /etc/mysql/mysql.conf.d/mysqld.cnf and add:

[mysqld]
sql_mode=""

Restart MySQL:

sudo systemctl restart mysql

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3. Check Autocommit and Transactions

If your application uses transactions but does not commit them, writes will not persist. Test this by running a simple query in your application to explicitly commit a transaction:

BEGIN;
INSERT INTO your_table (column1, column2) VALUES ('value1', 'value2');
COMMIT;

If this works, ensure your application is committing transactions where required.

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4. Enable MySQL General Query Log

To see all queries executed by your application, enable the general query log. This can help you identify the issue with the SQL queries.

Temporary Method:

SET GLOBAL general_log = 'ON';
SET GLOBAL general_log_file = '/var/log/mysql/general.log';

Permanent Method:

Edit /etc/mysql/mysql.conf.d/mysqld.cnf:

[mysqld]
general_log = 1
general_log_file = /var/log/mysql/general.log

Restart MySQL:

sudo systemctl restart mysql

Check the logs for write queries and errors:

sudo tail -f /var/log/mysql/general.log

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5. Enable MySQL Error Logging

MySQL logs errors to the error log file by default. To ensure logging is enabled, check your MySQL configuration:

1. Locate your error log file:

sudo cat /etc/mysql/mysql.conf.d/mysqld.cnf | grep log_error

• It should point to a file, such as /var/log/mysql/error.log.

2. If the file doesn’t exist, add the following to /etc/mysql/mysql.conf.d/mysqld.cnf:

[mysqld]
log_error = /var/log/mysql/error.log

3. Restart MySQL:

sudo systemctl restart mysql

4. Monitor the error log for issues:

sudo tail -f /var/log/mysql/error.log

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6. Application Debugging

Ensure your application is not silently failing. Common causes include:

• Validation rules in the application rejecting data before executing the query.
• Query failures due to constraints like foreign key relationships or unique indexes.
• Misconfigured database drivers.

Enable debug mode in your application to capture detailed error messages:

• For PHP/Laravel: Set APP_DEBUG=true in .env.