In SQL, the "COALESCE" and "ISNULL" functions are used to handle null values. Both functions allow you to specify a default value to use in place of nulls, but they work in slightly different ways.
The "COALESCE" function returns the first non-null value in a list of arguments. For example:
This would return 'default value', because it is the first non-null value in the list.
On the other hand, the "ISNULL" function returns a Boolean value indicating whether a value is null or not. For example:
This would return '1', because the value is null.
So, the main difference between "COALESCE" and "ISNULL" is that "COALESCE" returns a default value for nulls, while "ISNULL" returns a Boolean value indicating whether a value is null or not.
Both "COALESCE" and "ISNULL" can be useful in different situations. For example, you might use "COALESCE" to replace null values with a default value in a query, while you might use "ISNULL" to filter out null values or to perform a specific action when a value is null.
It's important to choose the appropriate function based on your specific needs and the context of your query.
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