Query to get all database name in SQL Server?

To get list of all database using query in SQL Server, use below query

SELECT name FROM master.sys.databases

You will see output like below

If you want list all sql server database name with there size, you can execute query below

    SELECT      sys.databases.name,  
                CONVERT(VARCHAR,SUM(size)*8/1024)+' MB' AS [Total disk space]  
    FROM        sys.databases   
    JOIN        sys.master_files  
    ON          sys.databases.database_id=sys.master_files.database_id  
    GROUP BY    sys.databases.name  
    ORDER BY    sys.databases.name  

Which will give you both database name and there size, as shown below

Source: Check database size in Sql server ( Various Ways explained)

Another query to list of all database excluding non-user database

SELECT name FROM master.sys.databases WHERE name NOT IN ('master', 'tempdb', 'model', 'msdb');

Above query will exclude database name like "master", "tempdb" etc, which aren't created by user.

You can also simply use below sql query to get database name in SQL Server

SELECT DB_NAME() AS DatabaseName

Will return all database names.