How Can I Implement Conditional Logic in SQL to Prioritize Data Retrieval?

Alternative Methods for Conditional Logic in SQL

Understanding the Problem

Conditional logic in programming languages allows branching based on specific conditions. In the given scenario, the task is to retrieve data from a table based on a priority system. If a condition is met, the query should return a specific set of rows, excluding any others that also meet the condition.

Solution: IF-Else Statements Using Subqueries

To achieve this in SQL, you can employ the following strategy:

IF ((SELECT COUNT(*) FROM table1 WHERE project = 1) > 0) 
    SELECT product, price FROM table1 WHERE project = 1
ELSE IF ((SELECT COUNT(*) FROM table1 WHERE customer = 2) > 0) 
    SELECT product, price FROM table1 WHERE customer = 2
ELSE IF ((SELECT COUNT(*) FROM table1 WHERE company = 3) > 0)
    SELECT product, price FROM table1 WHERE company = 3

Explanation

This query:

1. Executes subqueries to check the existence of data based on each condition.
2. Uses nested IF statements to determine which branch of the conditional logic to execute.
3. Returns the data based on the first condition that is met, preventing redundant data retrieval.

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