PostgreSQL provides some statements that assist users in decision-making scenarios. These statements take a decision on some specific criteria/condition and are hence referred to as control statements. In Postgres, the if-statement is one of the most valuable and frequently used control statements. The If statement executes only those expressions that satisfy the specified condition.

This post will present a thorough overview of the PostgreSQL if-statement with examples. So, let’s begin.

How to Use IF Statement in PostgreSQL?

In Postgres, the IF-statement only treats the true condition. The syntax of the IF statement is as follows:

IF condition 
THEN statement; 
END IF;

Here, condition represents a criterion that must be satisfied to execute the statements specified within the THEN block. If an expression doesn’t satisfy the specified criteria, then the if-statement moves the control to the next statement.

Example #1: How Does the IF Statement Work in PostgreSQL?

Let’s consider a scenario to understand the working of the IF statement:

DO $$ DECLARE 
user_age INT := 25;
BEGIN
IF user_age > 18 THEN
RAISE NOTICE 'Access Granted';
END IF;
IF user_age < 18 THEN
RAISE NOTICE 'Access Denied';
END IF;
END $$;

- Firstly, we utilized the DO statement which indicates that we are going to execute all the statements that come under the DO statement.

- Next, we declared a variable user_age and assigned it a value 25.

- After we utilized the BEGIN statement to start the execution.

- Next, we utilized the IF statement that checks if the user_age > 18. If yes, then show a message “Access granted”.

- If no, then the control will be moved to the next statement after the END IF where the variable’s value will be tested against the second condition i.e. user_age < 18.

The output authenticates the working of the if statement as it produced the accurate results.

Example #2: Working of IF statement in PostgreSQL?

Let’s modify the variable’s value and see how the if-statement work in that case:

DO $$ DECLARE
user_age INT := 15;
BEGIN
IF user_age > 18 THEN
RAISE NOTICE 'Access Granted';
END IF;
IF user_age < 18 THEN
RAISE NOTICE 'Access Denied';
END IF;
END $$;

This time the variable’s value will be tested against the first condition i.e. user_age > 18.

- The if-statement will return false, so the statements associated with the first condition will be skipped.

- The control will be moved to the second condition i.e. user_age<18.

- The if statement will compare the user’s age with the specified condition, i.e. 15 < 18.

- Consequently, it will return the following output:

The notice “Access Denied” authenticates the working of the IF statement.

Conclusion

In PostgreSQL, the if-statement is one of the most valuable and frequently used control statements. The If statement executes only those expressions that satisfy the specified condition. If an expression doesn’t satisfy the specified criteria, then the if-statement moves the control to the next statement. This post considered a couple of examples to explain the working of the if statement in Postgres.