In your experience with SQL, which of the following lists common types of JOINs that are widely used to combine related data from multiple tables?

Introduction / Context:
Structured Query Language provides several types of JOINs to combine rows from two or more tables based on related columns. Each join type defines how rows are matched and whether non matching rows are included in the result set. Understanding these join types is fundamental to database querying and is frequently tested in interviews. This question asks you to identify a list of common join types that are widely used in practice.

Given Data / Assumptions:

• We are working with relational databases that support standard join syntax.
• Join types are defined by how they include matched and unmatched rows from participating tables.
• The question focuses on conceptual names such as inner, outer, and cross joins.
• Some options list fictional join names for contrast.

Concept / Approach:
The most commonly used join types in SQL are INNER JOIN, LEFT OUTER JOIN, RIGHT OUTER JOIN, FULL OUTER JOIN, and CROSS JOIN. INNER JOIN returns rows where there is a match in both tables. LEFT OUTER JOIN returns all rows from the left table and the matching rows from the right table, filling unmatched columns with nulls. RIGHT OUTER JOIN is similar but returns all rows from the right table. FULL OUTER JOIN returns all rows from both tables, with nulls where there is no match on either side. CROSS JOIN produces the Cartesian product of both tables, pairing every row from the first table with every row from the second. Together, these join types cover most typical scenarios for combining related data.

Step-by-Step Solution:
Step 1: Recall that INNER JOIN, LEFT OUTER JOIN, RIGHT OUTER JOIN, FULL OUTER JOIN, and CROSS JOIN are standard Structured Query Language join types. Step 2: Recognise that option a lists exactly these well known join types. Step 3: Observe that options b, c, and d use invented or humorous join names that are not part of the Structured Query Language specification. Step 4: Select option a as the list that correctly reflects common joins used in real SQL queries. Step 5: Confirm that other options contain no recognised Structured Query Language join terms.

Verification / Alternative check:
Database documentation, tutorials, and query examples consistently describe these five join types. Many graphical query tools present them as choices when building joins visually. They can be combined with ON conditions and sometimes with USING clauses, but the underlying types remain the same. The absence of terms like Top Join or Round Join in official documentation confirms that option a is the correct list.

Why Other Options Are Wrong:
Options b, c, and d are composed of fictional join names such as Top Join, Square Join, and Maybe Join. These are not valid Structured Query Language keywords and will not be recognised by any standard relational database engine. They are included here to test whether you can distinguish real join types from made up ones.

Common Pitfalls:
A common pitfall is to rely exclusively on INNER JOIN and LEFT OUTER JOIN, ignoring other join types that may be better suited for certain reporting requirements. Another issue is confusion between FULL OUTER JOIN and UNION, which are distinct operations. For exam questions, knowing the names and high level behaviour of INNER, LEFT, RIGHT, FULL, and CROSS joins is usually sufficient, as listed in option a.

Final Answer:
Commonly used join types include INNER JOIN, LEFT OUTER JOIN, RIGHT OUTER JOIN, FULL OUTER JOIN, and CROSS JOIN, which are the join types listed in option a.