Learn SQL’s CAST Function for Clean Type Conversion

Data types matter in SQL. Whether you’re comparing values or formatting results, type mismatches can cause problems. That’s where the CAST function comes in—it converts data types explicitly, cleanly, and consistently. Let’s look at how to use it effectively.

CAST Examples

String to Integer

SELECT CAST('100' AS INT);

Float to INT

SELECT CAST(42.69 AS SIGNED);

INT to Decimal

SELECT CAST(3 AS DECIMAL);

String to Date

SELECT CAST('2024-12-21' AS DATE);

INT to String

SELECT CAST(42 AS CHAR);

Best Practices

• Use CAST when explicit conversion improves clarity.
• Avoid casting unless required—some conversions happen automatically.
• Prefer date-specific functions for formatting over generic casting.
• Be cautious with numeric rounding.

FAQ

• Is CAST cross-database?

  Yes, it follows the SQL standard.

• Can every type be cast?

  Only compatible ones—check your DB docs.

• CAST vs CONVERT vs ::?

  CAST is standard. CONVERT is SQL Server. :: is PostgreSQL-only.

• What if CAST fails?

  Usually returns NULL or triggers an error.

Conclusion

SQL's CAST function is your go-to tool for converting values clearly and safely across database platforms. Mastering it helps you write better queries and handle mixed data with confidence. Want to simplify conversions even further? Try DbVisualizer to inspect and convert data visually. Read SQL CAST Function: Everything You Need to Know article for more insights.