What is MySQL's `` Operator and How Does it Handle NULL Values?

MySQL's Operator : A Comprehensive Guide**

MySQL offers a unique operator, , distinct from the standard relational operators. Understanding its significance is crucial for working with MySQL queries, especially when dealing with NULL values.

What is the Operator?**

The operator is the MySQL-specific NULL-safe equal operator. Similar to the regular = operator, it compares two values and returns 0 if they are not equal or 1 if they are equal. The key difference lies in its handling of NULL values.

Handling of NULL Values

Unlike the = operator, does not treat NULL values as special. This means that:

1. 'a' NULL** yields 0, indicating inequality.
2. NULL NULL** yields 1, indicating equality.

Usefulness of the Operator**

The operator is particularly valuable when dealing with data that may contain NULL values. It ensures that the comparison results are consistent, regardless of the presence or absence of NULL values.

For instance, in the following query:

WHERE p.name **** NULL

The operator ensures that records with NULL values for the p.name column will not be excluded from the query results. Instead, they will be considered equal to NULL.

Related Operators

MySQL also provides other NULL-related operators:

1. IS NULL: Tests if a value is NULL.
2. IS NOT NULL: Tests if a value is not NULL.

These operators, which are part of the ANSI standard, offer alternative ways to compare against NULL. However, they are not as convenient as in all situations.

Portability Considerations

The operator is a MySQL-specific feature. For portable code, consider using the following alternatives:

1. IS [NOT] DISTINCT FROM: Introduced in SQL:2003, this predicate works similarly to .
2. CASE WHEN (a = b) or (a IS NULL AND b IS NULL) THEN 1 ELSE 0 END = 1: A more complex but universally supported expression.

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