SQL : BETWEEN vs <= and >=

SQL: Understanding BETWEEN vs. <= and >=

Explore the nuances of using the BETWEEN operator versus a combination of less than or equal to (<=) and greater than or equal to (>=) in SQL queries. Learn when to use each for optimal clarity and performance.

In SQL, filtering data based on a range is a common operation. Two primary methods exist for this: the BETWEEN operator and the combination of comparison operators (<= and >=). While they often produce identical results, understanding their subtle differences, including how they handle boundary conditions and NULL values, is crucial for writing robust and readable SQL queries. This article delves into these distinctions, providing practical examples and best practices.

The BETWEEN Operator: Inclusive Range Filtering

The BETWEEN operator in SQL is used to select values within a specified range. It is inclusive, meaning it includes both the start and end values of the range. The syntax is straightforward: expression BETWEEN value1 AND value2. It's often favored for its readability when dealing with date, numeric, or string ranges.

SELECT ProductName, Price
FROM Products
WHERE Price BETWEEN 10.00 AND 20.00;

Using BETWEEN to filter prices between 10.00 and 20.00 (inclusive).

Comparison Operators: Explicit Range Definition

Alternatively, you can achieve the same inclusive range filtering using a combination of the greater than or equal to (>=) and less than or equal to (<=) operators, joined by AND. The syntax is expression >= value1 AND expression <= value2. This method offers explicit control over each boundary condition and can sometimes be more intuitive for developers who prefer direct logical expressions.

SELECT ProductName, Price
FROM Products
WHERE Price >= 10.00 AND Price <= 20.00;

Using >= and <= to filter prices between 10.00 and 20.00 (inclusive).

Handling NULL Values and Performance Considerations

Both BETWEEN and the combination of >= and <= behave similarly with NULL values: if any part of the comparison (the expression or either of the range values) is NULL, the entire condition evaluates to UNKNOWN, and the row will not be returned. From a performance standpoint, modern SQL optimizers are typically smart enough to treat both constructs identically, resulting in similar execution plans. Therefore, the choice often boils down to readability and specific edge case handling.

flowchart TD
    A[Start Query]
    B{Is value BETWEEN value1 AND value2?}
    C{Is value >= value1 AND value <= value2?}
    D[Return Row]
    E[Skip Row]

    A --> B
    B -- Yes --> D
    B -- No --> E

    A --> C
    C -- Yes --> D
    C -- No --> E

Conceptual flow of BETWEEN vs. comparison operators for range filtering.