COALESCE returns the first non-NULL value from a list of expressions. It is useful with JOINs when unmatched records produce NULL values.
Outer JOINs can produce NULL values for missing related records. COALESCE can replace those NULL values with meaningful defaults.
Display zero instead of NULL for customers who have no orders.
SELECT
c.CustomerName,
COALESCE(SUM(o.OrderAmount), 0) AS TotalSales
FROM Customers c
LEFT JOIN Orders o
ON c.CustomerID = o.CustomerID
GROUP BY c.CustomerName;COALESCE with JOIN is useful in sales reports, financial dashboards, customer analysis, reconciliation, and data-quality reporting.
- COALESCE returns the first non-NULL value.
- It is useful with OUTER JOINs.
- It can replace missing values with defaults.
- COALESCE can be used with aggregate results.
- It improves report readability.
Why use COALESCE with JOIN?
COALESCE can replace NULL values created by unmatched rows with a meaningful default value.
What does COALESCE return?
COALESCE returns the first non-NULL expression from the values provided.