Sql Statement

Deletion / Updates

A deletion statement consists of: 1. The keywords DELETE FROM, 2. The name of a relation, say R, 3. The keyword WHERE, and 4. A condition. That is, the form of a deletion is DELETE FROM R WHERE ; The effect of executing this statement is that every tuple satisfying the condition (4) will be deleted from relation R.

Deferring the Checking of Constraints

Suppose the situation of "Declaring Foreign-Key Constraints" Example 1, where presC# in Studio is a foreign key referencing cert# of MovieExec. Bill Clinton decides, after his national presidency, to found a movie studio, called Redlight Studios, of which he will naturally be the

Procedures Stored in the Schema

In this section, we introduce you to a recent SQL standard called Persistent, Stored Modules (SQL/PSM, or just PSM, or PSM-96). Each commercial DBMS offers a way for the user to store with a database schema some functions or procedures that can be used in SQL queries

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