coalesce in PostgreSQL — Examples & 2025 Guide

The COALESCE function in PostgreSQL is a powerful SQL tool for handling NULL values—making your data cleaner, reports more accurate, and queries easier to maintain. It returns the first non-NULL value in a list, helping developers and analysts avoid messy NULLs in output.

Despite its simplicity, many users struggle with effectively integrating COALESCE into larger queries or reporting pipelines. That’s where AI2sql comes in: just describe your logic in plain English, and AI2sql instantly generates the correct COALESCE SQL, saving hours of frustration and ensuring consistent, error-free results.

Understanding COALESCE

• Syntax: COALESCE(value1, value2, ...)

• Main benefit: Replace or bypass NULLs without nested CASE statements

• Common use cases: Data reporting, fallback/default values, concatenating nullable fields

Real-World Examples: COALESCE in PostgreSQL

1. Simple Column Default

SELECT COALESCE(phone, 'N/A') AS contact_number FROM customers;

2. Combining Multiple Nullable Fields

SELECT name, COALESCE(email, secondary_email, 'no_email@sample.com') AS preferred_email FROM users;

3. Using COALESCE with Aggregates

SELECT department, COALESCE(SUM(sales), 0) AS total_sales FROM orders GROUP BY department;

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Benchmark: Manual vs AI2sql COALESCE Queries (Mini Table)

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FAQ: COALESCE in PostgreSQL

• Q: What is the main difference between COALESCE and NVL?
  A: COALESCE is ANSI-standard and can take multiple arguments; NVL is Oracle-specific and supports only two.

• Q: Can COALESCE handle more than two arguments?
  A: Yes, it checks each value in order and returns the first non-NULL.

• Q: Is COALESCE efficient in large datasets?
  A: Yes—it's optimized internally by PostgreSQL and is recommended for handling NULLs.

• Q: Does AI2sql support other NULL-handling strategies?
  A: Absolutely! The AI2sql platform supports all NULL logic, CASE statements, and more.

• Try AI2sql COALESCE Generator

• COALESCE in PostgreSQL Tutorial

• COALESCE in PostgreSQL Examples

COALESCE gives your reports reliability and your code readability. With AI2sql, leveraging this essential PostgreSQL function is fast, accurate, and effortless—whether you're maintaining dashboards or building data pipelines.

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