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221. COALESCE Function

Learn how to return the first non-NULL value from multiple expressions.

📘 Lesson 221 of 728 ⏱ 9 min 🎯 Intermediate

The COALESCE function evaluates expressions from left to right and returns the first value that is not NULL.

Real-world databases often contain missing values. COALESCE allows analysts to provide fallback values and make query results easier to interpret.

Display a customer's phone number and use an alternate phone number when the primary number is missing.

SQL 
SELECT
    CustomerName,
    COALESCE(Phone, AlternatePhone, 'Not Available') AS ContactNumber
FROM Customers;

COALESCE is widely used for data cleaning, reporting, fallback values, and handling missing business information.

  • COALESCE handles NULL values.
  • It checks expressions from left to right.
  • It returns the first non-NULL value.
  • It can accept multiple expressions.
  • It is useful for fallback values.
What does COALESCE do?

COALESCE returns the first non-NULL value from a list of expressions.

Why is COALESCE useful?

It helps handle missing values and provides fallback values when the preferred value is NULL.

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