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430. JOIN with COALESCE

Learn how COALESCE can replace NULL values in joined results with useful fallback values.

📘 Lesson 430 of 728 ⏱ 11 min 🎯 Intermediate

COALESCE returns the first non-NULL expression from a list of expressions and is useful for handling missing values produced by joins.

Outer joins commonly produce NULL values when related records do not exist. COALESCE can provide clearer report output.

Display 'No Order' when a customer has no matching order.

SQL 
SELECT
    c.CustomerName,
    COALESCE(o.OrderID, 'No Order') AS OrderStatus
FROM Customers c
LEFT JOIN Orders o
    ON c.CustomerID = o.CustomerID;

COALESCE with JOIN is useful in customer reports, reconciliation, dashboards, and data-quality reporting.

  • COALESCE returns the first non-NULL value.
  • It is useful after OUTER JOINs.
  • It can provide fallback values.
  • It improves report readability.
  • COALESCE can accept multiple expressions.
Why use COALESCE with LEFT JOIN?

COALESCE can replace NULL values created by unmatched right-side records with a meaningful fallback value.

What does COALESCE return?

It returns the first expression in the list that is not NULL.

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