As shown earlier, the Table input step is the option to read data from a database. The SQL area is where you write the SELECT statement that will generate your dataset.
When you add a Table input step, it comes with a default SELECT statement for you to complete:
SELECT <values> FROM <table name> WHERE <conditions>
If you need to query a single table, you can take advantage of the Get SQL select statement... button, which generates the full statement for you. After you get the statement, you can modify it at your will. If you need to write more complex queries, you definitively have to do it manually.
You can write any Select query as far as it is a valid SQL statement for the selected type ...
