Here you can check SQL queries for compliance with the TYPO3 SQL parser. If you enter values in the form fields those are handed to the query building methods and the result is shown. Check of it matches your input to see if the DB subsystem (core and DBAL) can do what you want. For testing inserts, a very simple syntax is used to specify the values to be inserted in the first text area: Each line is seen as a key/value pair that is exploded at =.
The raw SQL check allows you to enter any query you like and have it parsed and reassembled by TYPO3. If this is successful the input will be shown below. In case of an error (input and output not matching) the query generated by TYPO3 is shown in a red box below the input query.