SQL ISNULL() Explained

Some RDBMSs provide an ISNULL() function that can be used when dealing with potentially null values.

MySQL, MariaDB, and Oracle Database each have an ISNULL() function that returns 1 if its argument is null, and 0 if it’s not.

SQL Server also has an ISNULL() function, but it works differently. It works more like how the IFNULL() function works in some other RDBMSs.

Other RDBMSs, such as PostgreSQL and SQLite don’t include an ISNULL() function, but they do support the IS NULL predicate (as do the other RDBMSs).

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