Interpretive Database EXISTS and Null Predicate Algorithms
Original Publication Date: 1988-Oct-01
Included in the Prior Art Database: 2005-Feb-15
The Structured Query Language (SQL) developed for use with relational database systems is used to describe database operations to the IBM Database Manager. Predicate testing is an integral part of database operations and is used to determine which rows of a given table satisfy the criteria specified by the user of the database. One such predicate is the comparison of a data value with column values of a table to determine if the data value is represented in the table. Another such function is the test for a null data value. (Image Omitted) Other database products employ a system of control blocks which implement control functions and record accesses specified by a given SQL statement. These control blocks are subsequently manipulated by control block specific functions at execution time.