What is the method for determining null values within a given dataset using SQL?

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There are several ways to determine null values within a given dataset using SQL, depending on the specific database management system being used. Some common methods are:

1. Using the IS NULL operator: SELECT * FROM table WHERE column IS NULL;

This query will return all rows from the table where the specified column has a null value.

1. Using the COUNT function: SELECT COUNT(*) FROM table WHERE column IS NULL;

This query will return the number of rows in the table where the specified column has a null value.

1. Using the GROUP BY clause: SELECT column, COUNT() FROM table GROUP BY column HAVING COUNT() > 0;

This query will group the data by the specified column and return the number of non-null values for each group. It will exclude groups with no non-null values.

1. Using the NULLIF function: SELECT * FROM table WHERE NULLIF(column, '') IS NULL;

This query will return all rows from the table where the specified column has either a null value or an empty string. The NULLIF function is used to convert empty strings to null values for comparison.