The expression editor helps you create advanced SQL.
At the top is a text area with your SQL. You can directly type into this area at any time. Below this are buttons to add operators and other text to the SQL text. Below this is a tabbed view that gives you access to all functions, columns, and values in the datasource you are connected to. A split bar allows you to adjust the size of these areas to suit your needs.
The tabbed view assists in three areas
The functions tab shows all functions that are known for the datasource. They are catagorized by type so finding a desired function can be quick. For example if the character column in our query may have extra trailing or leading blanks, we can apply the trim function to the values returned from that column. We select the desired trim function from the list of available functions, select the item we wish to trim -- the Customer column,
and press the "wrap" button.
The columns tab will display all the tables currently in the query. For each table it displays the columns it contains, and when one is selected, the type of data that the column contains. Press the insert button to add the column to the SQL text wherever you have put the text cursor.
The distinct values tab displays a tree of all tables currently in the query and their columns. Click on a column to see the distinct values it contains. Returned values appear in the right list. Returned values can be selected and then inserted into the SQL text as desired.