SQL Server’s COALESCE simplifies dealing with NULL values by returning the first non-NULL expression. It’s a versatile tool for improving data handling in queries.
Use cases for coalesce
Default placeholders, replace NULL for better reporting.
SELECT COALESCE(Address, 'N/A')
FROM Employee;
Sorting without NULL issues, avoid unexpected order results.
SELECT COALESCE(Discount, 0)
FROM Product ORDER BY Discount;
Consistent calculations, prevent errors in math.
SELECT Price * (1 - COALESCE(Discount, 0)/100) AS FinalPrice
FROM Product;
FAQ
What does COALESCE do in SQL Server?
It returns the first non-NULL value in a list of expressions.
Does COALESCE work in other databases?
Yes, it’s ANSI SQL-compliant and widely supported.
What’s the difference between COALESCE and ISNULL?
COALESCE supports multiple arguments; ISNULL replaces only one.
Is COALESCE efficient?
It can be. Minimize arguments and prioritize non-NULL values for best performance.
Summary
The COALESCE function simplifies managing NULL values and ensures reliable results. Learn more in the article A Complete Guide to the SQL Server COALESCE Function.
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