In SQL, for what purpose is the BETWEEN keyword primarily used in a WHERE clause when filtering query results?

Introduction / Context:
The BETWEEN keyword is a common part of the SQL language and frequently appears in certification questions. It is used to simplify conditions in the WHERE clause when you need to test whether a value lies within a continuous range. Understanding how BETWEEN works, including its inclusive behavior on both boundaries, is important for writing accurate queries and avoiding off by one or off by boundary errors.

Given Data / Assumptions:

• The question concerns the SQL BETWEEN keyword.
• The context is a WHERE clause that filters rows from a table or result set.
• No specific database vendor is assumed; standard SQL behavior is considered.
• The goal is to identify the primary purpose of BETWEEN, not secondary or unrelated behaviors.

Concept / Approach:
In standard SQL, BETWEEN is used to check whether an expression value lies within a given range. The syntax usually looks like expression BETWEEN low_value AND high_value. The important points are that BETWEEN is inclusive of both the low and high values and that it replaces a longer expression using greater than or equal to and less than or equal to operators. It is not a wildcard operator, it does not control which columns appear in the SELECT list, and it does not directly join tables.

Step-by-Step Solution:
Step 1: Recall that a typical use looks like WHERE salary BETWEEN 30000 AND 50000, which returns all rows where salary is at least 30000 and at most 50000. Step 2: Understand that this condition is logically equivalent to salary >= 30000 AND salary <= 50000. Step 3: Recognize that this behavior clearly describes a range filter over numeric values, dates, or other comparable data types. Step 4: Compare this understanding against the answer choices and select the one that correctly states that BETWEEN is used to select values within an inclusive range.

Verification / Alternative check:
You can verify by considering a date example: WHERE order_date BETWEEN '2024-01-01' AND '2024-01-31' returns orders from the first through the thirty first of January, including both dates. If you replace BETWEEN with greater than and less than or equal conditions, you get the same result. This confirms that BETWEEN is a convenient shorthand for inclusive range checks in the WHERE clause.

Why Other Options Are Wrong:
Option B is wrong because wildcard matching uses operators like LIKE along with characters such as percent and underscore, not BETWEEN. Option C is incorrect since the columns displayed in the query output are controlled by the SELECT list, not by BETWEEN. Option D is clearly incorrect because table joins are performed using JOIN clauses and join conditions, not by using BETWEEN in the WHERE clause for numeric ranges.

Common Pitfalls:
A common mistake is forgetting that BETWEEN is inclusive of both endpoints. For numeric and date comparisons, this can lead to boundary errors if you intended an exclusive range. Another pitfall is assuming that BETWEEN always performs better than equivalent comparison operators; in practice, query optimizers handle both forms similarly. Knowing the inclusive nature of BETWEEN and using it only for proper range comparisons will make your SQL queries clearer and easier to maintain.

Final Answer:
The BETWEEN keyword is primarily used to select rows where a column value falls within a specified inclusive range between a lower bound and an upper bound.