The DP4 SQL interface supports queries and updates in the SQL language. You can enter the commands interactively, or as text files.
You use the SQL to specify the conditions under which records are extracted. Where records are extracted from more than one table, SQL 'joins' the records from the tables.
To update the database in SQL, you can define an input file and specify a cursor that indicates the next record to be read. Records can be inserted into the database, and amended or deleted according to a condition.