What is the use of predicate?

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Predicates are used to enhance the performance of query.

In the context of databases, including DB2, a predicate is a condition or a set of conditions that are used to filter or qualify the rows retrieved from a database table. Predicates are commonly used in SQL queries to specify the criteria for selecting data.

For example, in a SELECT statement, the WHERE clause typically contains predicates that define the conditions for filtering the rows. Here’s a simple example:

SELECT *
FROM employee
WHERE salary > 50000;

In this example, the salary > 50000 is a predicate that filters the rows from the “employee” table where the salary is greater than 50000.

Predicates can also be used in other parts of SQL statements, such as JOIN conditions or HAVING clauses. They play a crucial role in defining the criteria for retrieving, updating, or deleting data from a database.

So, to answer the question directly: The use of a predicate in DB2 (or any other relational database) is to specify conditions that filter or qualify the rows retrieved from a table in SQL queries.