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: 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: 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: 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: 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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