PostgreSQL IF Statement: Conditional Logic in SQL
Learn how to use conditional logic in PostgreSQL with the IF statement. Includes syntax, examples, and tips for efficient conditional database operations.
PostgreSQL IF Statement
PostgreSQL does not have a direct IF statement for use within SQL queries. However, conditional logic can be achieved using:
1. PL/pgSQL Blocks:
The IF statement is available in PL/pgSQL blocks for procedural logic.
2. CASE Expression:
For inline conditional logic in SQL queries.
Using IF in PL/pgSQL
The IF statement in PL/pgSQL allows developers to execute conditional operations within a procedural block.
Syntax:
DO $$
BEGIN
IF condition THEN
-- Statements to execute if condition is true
ELSIF other_condition THEN
-- Statements for the next condition
ELSE
-- Statements if no condition matches
END IF;
END;
$$ LANGUAGE plpgsql;
Example:
Code:
DO $$
BEGIN
IF EXISTS (SELECT 1 FROM users WHERE email = '[email protected]') THEN
RAISE NOTICE 'User exists';
ELSE
RAISE NOTICE 'User does not exist';
END IF;
END;
$$ LANGUAGE plpgsql;
Explanation:
Using CASE in SQL Queries
The CASE expression allows for inline conditional evaluations within a query.
Syntax:
SELECT
CASE
WHEN condition THEN result
ELSE default_result
END
FROM table_name;
Example:
Code:
SELECT
user_id,
CASE
WHEN age < 18 THEN 'Minor'
WHEN age BETWEEN 18 AND 60 THEN 'Adult'
ELSE 'Senior'
END AS age_group
FROM users;
Explanation:
Advanced Tips
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