IN vs. ANY in PostgreSQL: When Should I Use Each Operator?

PostgreSQL IN and ANY Operators: A Detailed Comparison

PostgreSQL offers both IN and ANY operators for comparing a column value against a set of values. While functionally similar, key differences exist impacting query performance and flexibility.

Functional Equivalence

Fundamentally, IN is equivalent to = ANY. Both check if a column value matches any value within a defined set. For instance:

SELECT * FROM my_table WHERE id IN (1, 2, 3);
SELECT * FROM my_table WHERE id = ANY ('{1, 2, 3}');

These queries yield identical results.

Syntax Variations

Both operators have distinct syntaxes:

• IN (set): Uses parentheses to enclose a comma-separated list of values.

   SELECT * FROM my_table WHERE id IN (1, 2, 3);

• ANY (set): Employs curly braces to encapsulate a set of values (typically an array).

   SELECT * FROM my_table WHERE id = ANY ('{1, 2, 3}');

Data Type Handling: Arrays vs. Lists

A crucial distinction lies in how they handle input:

• IN accepts a comma-separated list, potentially mixing data types.
• ANY expects an array, requiring a predefined data type.

This difference can affect performance and data type constraints.

ANY's Enhanced Versatility

ANY surpasses IN in versatility. It pairs with various operators beyond =, for example:

SELECT * FROM my_table WHERE name LIKE ANY ('{John, Mary, Joe}');

Performance Aspects

For extensive value sets, ANY with arrays generally exhibits better scalability compared to IN with comma-separated lists.

Negation and Exclusion

To exclude rows where a column value is within a set:

• IN: Use NOT IN (1, 2, 3)
• ANY: Employ id <> ALL ('{1, 2, 3}')

Handling NULL values in exclusions demands careful consideration, often requiring explicit IS NOT TRUE checks:

SELECT * FROM my_table WHERE (id = ANY ('{1, 2, 3}')) IS NOT TRUE;

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