They take care of security and maintain backups of data. Execution of SQL commands can be done by SQL developers but the changes should be approved by the DBA, because ultimately they are responsible for maintaining the structure and security of the database. Developers should not create the SQL commands as this may lead to data conflicts, sometimes they may not be aware of the complete structure of the database. For example, if you need to write a query that generates reports, if the application developer writes the query it can only be used in the application but if a SQL developer writes the query it can be used by the application developer and also independently to generate reports. Because the SQL developer places queries into the database as a view that is accessed by the developer and others. End users should not query, as they may not even be aware of the structure other than understanding the functionality. Basic troubleshooting queries can be run by the DBA, but when a bigger problem occurs SQL developers can fix them since they have a better understanding of the low level