In the 'SQL' tab you can enter SQL statements. The fields of the active table (here 'activity') are displayed. You can select a field name and add '<<' to the text box with the insert button. The field name is surrounded by 'backticks' (right-pointing single quotes). You can omit the reversed single quotes. Click on the 'Start' button to run the SQL query.

If you click on the 'Console' button at the bottom, you can enter a query at the MySQL prompt.
Pressing CTRL+Enter executes the query. The result appears above it in the display window.