SQL Statements

Various standards for the SQL language exist. The DP4 SQL implementation attempts to satisfy, as far as practicable, two of the better known ones, namely the then ANSI SQL2 standard (1992) and the IBM SAA standard (i.e. DB2). Any departures from these are mainly due to the different data types and underlying database structure of the DP4 RDBMS.

The many restrictions on the language specified in the ANSI standard, may seem arbitrary, but are also reflected in the DP4 implementation to simplify the internal working of the DP4 SQL Engine. However, some statements that are illegal according to the standard, but which have an obvious interpretation are, in fact, accepted by the DP4 system. Other than the differences between the DP4 implementation and the ANSI and IBM standards and a few minor enhancements, no attempt has been made to extend the language described by the standards.

The SQL data manipulation statements fall into two categories:

• Non-cursor operations:

  • SELECT
  • INSERT
  • UPDATE (searched update)

  • DELETE (searched delete)

• Transaction termination operations:

  • COMMIT WORK
  • ROLLBACK WORK