How to use the COALESCE function to handle NULL values in SQL queries?

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Aryan Kumar · Answer

You can use the COALESCE function in SQL to handle null values in queries by returning the first non-null value from a list of expressions. It's particularly useful when you want to replace null values with a default value or a value from another column. Here's the syntax for the COALESCE function:
COALESCE(expression1, expression2, expression3, ...)
expression1, expression2, expression3, and so on are the values or columns you want to evaluate. The function returns the first non-null expression from left to right.
Here are a few common use cases for the COALESCE function:
Replace Null with a Default Value:
Suppose you have a column named price, and you want to display a default value of 0 when it's null:
SELECT COALESCE(price, 0) AS adjusted_price
FROM products;
In this query, if price is null, it will be replaced with 0 in the result set.
Select the First Non-Null Value from Multiple Columns:
You can use COALESCE to select the first non-null value among multiple columns. For example, if you have columns
first_name and last_name and you want to display the first non-null name:
SELECT COALESCE(first_name, last_name) AS full_name
FROM users;
If first_name is null, it will display the value from 
last_name as full_name.
Handle Nested Nulls:
You can nest COALESCE functions to handle situations where multiple columns may contain null values:
SELECT COALESCE(col1, COALESCE(col2, col3, col4, 'No value')) AS result
FROM your_table;
This query checks col1 first, and if it's null, it checks 
col2, and so on. If all columns are null, it returns 'No value'.
The COALESCE function is a powerful tool for handling null values and providing default values or alternate values in SQL queries, making your results more informative and user-friendly.

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How to use the COALESCE function to handle NULL values in SQL queries?

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