Oracle and PL/SQL Recipes: A Problem-Solution Approach

2-13. Ensuring That Multiple Queries “See” the Same Data

Problem

You are issuing a set of queries against the database, and you need to ensure that none of the table rows changes throughout the course of the queries being made.

Solution

Set up a read-only transaction in which the current transaction will see the data only as an unchanged snapshot in time. To do so, use the SET TRANSACTION statement to begin a read-only transaction and establish a snapshot of the data so it will be consistent and unchanged from all other updates being made. For instance, the following example displays a block that sets up read-only queries against the database for dollar values from a bank account:

DECLARE    daily_atm_total   NUMBER(12,2);    weekly_atm_total  NUMBER(12,2); ...