SQL IF ELSE: Conditional Logic in Queries and Scripts

What Is SQL IF ELSE?

SQL IF ELSE is procedural control flow that executes one block when a Boolean condition is true and another when false. Standard SQL uses CASE inside a query, while vendors like T-SQL and PL/pgSQL add standalone IF ELSE for stored procedures and scripts.

When Should I Use IF ELSE Over CASE?

Use IF ELSE in procedural code—stored procedures, functions, or anonymous scripts—where you need to run multiple statements, variable assignments, or DDL. Use CASE inside a single SELECT to conditionally compute values without controlling statement flow.

How Does Basic IF ELSE Syntax Look in T-SQL?

The minimal pattern: IF <condition> BEGIN ... END ELSE BEGIN ... END. The condition is any expression that returns TRUE or FALSE. Blocks can contain any valid T-SQL, including SELECT, UPDATE, variable logic, or nested IFs.DECLARE @sales INT = 12000;
IF @sales >= 10000
BEGIN
UPDATE bonuses SET level = 'gold' WHERE rep_id = 7;
END
ELSE
BEGIN
UPDATE bonuses SET level = 'silver' WHERE rep_id = 7;
END;

Can I Nest Multiple IF Conditions?

Yes. Combine IF ELSE IF (or ELSEIF/ELSIF) to create multi-branch trees. Keep nesting shallow—three levels max—to preserve readability. Complex branching is better expressed as CASE in queries or as lookup tables.

How Do I Write IF ELSE in PostgreSQL Functions?

PL/pgSQL uses IF condition THEN ... ELSIF ... ELSE ... END IF; inside LANGUAGE plpgsql blocks. Each branch ends with a semicolon, and the entire structure ends with END IF;.CREATE OR REPLACE FUNCTION award_bonus(p_sales NUMERIC) RETURNS TEXT AS $$
DECLARE bonus TEXT;
BEGIN
IF p_sales >= 10000 THEN
bonus := 'gold';
ELSIF p_sales >= 5000 THEN
bonus := 'silver';
ELSE
bonus := 'bronze';
END IF;
RETURN bonus;
END;
$$ LANGUAGE plpgsql;

What Are Real-World Use Cases?

Common scenarios: applying tiered discounts, toggling feature flags, logging only on errors, early-exit validation in ETL, or choosing between INSERT and UPDATE in upsert logic.

Best Practices for IF ELSE Logic?

Place filtering conditions in SET-based queries first to minimize row counts. Keep blocks small and purpose-focused. Prefer CASE for column-level decisions. Document intent with comments, and include an ELSE branch to handle unexpected states.

How Does Galaxy Improve IF ELSE Development?

Galaxy’s AI copilot autocompletes IF ELSE scaffolds, suggests variable names, and warns when a condition lacks ELSE coverage. Inline linting surfaces unreachable code, and Collections let teams endorse approved branching patterns.