PostgreSQL if 0 then 1 - SQL

Introduction:

This article introduces you to the concept of the "if 0 then 1" in PostgreSQL SQL statements. This feature enables you to write conditional statements that always return a specified value, even if the condition is not met. The if 0 then 1 clause is particularly useful in situations where you need to return a default value for a certain condition.

Syntax:

The syntax of the "if 0 then 1" statement is as follows:

SELECT CASE WHEN condition THEN result ELSE 1 END FROM table;

In this statement, the "condition" is the expression to be evaluated, the "result" is the value to be returned when the condition is true, and "1" is the default value to be returned when the condition is false.

Example:

To illustrate the use of the "if 0 then 1" statement in PostgreSQL, consider the following example. Suppose you have a table called "students" that contains the following data:

student_id | name      | grade
-----------|-----------|-------
1          | John      | 85
2          | Sarah     | 92
3          | Michael   | 
4          | Jennifer  | 72
5          | Christopher | 89

If you want to select the grade of a student with a given student ID, but return a default value of 70 if the grade is null, you can use the following SQL statement:

SELECT CASE WHEN grade IS NOT NULL THEN grade ELSE 70 END FROM students WHERE student_id = 3;

The above statement will return 70 because the grade for the student with student_id = 3 is null. If the grade was not null, the statement would have returned the actual grade.

Conclusion:

The "if 0 then 1" clause in PostgreSQL SQL statements allows you to write conditional statements that always return a specified value, even if the condition is not met. This feature is useful in situations where you need to return a default value for a certain condition.