| 1 | What common mistakes do developers make when writing multi table joins that can lead to unexpectedly large or incorrect result sets? SQL Server › Joins | SQL Server | Joins | Intermediate |
| 2 | How should you structure Firestore data using subcollections and denormalization to design efficient queries, given that Firestore does not support traditional relational joins across separate collections? Flutter › Cloud Firestore & Firebase Storage | Flutter | Cloud Firestore & Firebase Storage | Advanced |
| 3 | What is an INNER JOIN, and how does it combine data from two tables? SQL Server › Joins | SQL Server | Joins | Beginner |
| 4 | What is the difference between a LEFT JOIN and a RIGHT JOIN? SQL Server › Joins | SQL Server | Joins | Beginner |
| 5 | How do you find rows that exist in one table but have no matching row in another table using a join? SQL Server › Joins | SQL Server | Joins | Intermediate |
| 6 | What is a FULL OUTER JOIN, and when would you use one instead of a LEFT or RIGHT JOIN? SQL Server › Joins | SQL Server | Joins | Intermediate |
| 7 | How does a CROSS JOIN work, and what are some legitimate use cases for it despite the risk of accidentally creating a huge result set? SQL Server › Joins | SQL Server | Joins | Advanced |
| 8 | How does SQL Server's query optimizer decide which physical join algorithm, such as nested loops, merge join, or hash join, to actually use for a given query? SQL Server › Joins | SQL Server | Joins | Advanced |
| 9 | How does the GROUP BY clause work together with aggregate functions? SQL Server › Aggregate Functions & GROUP BY | SQL Server | Aggregate Functions & GROUP BY | Beginner |
| 10 | How do you define multiple common table expressions within a single query? SQL Server › Common Table Expressions (CTEs) | SQL Server | Common Table Expressions (CTEs) | Beginner |
| 11 | What is a foreign key constraint, and how does it help maintain data integrity between two related tables? SQL Server › Constraints (Primary Key, Foreign Key, Check & Unique) | SQL Server | Constraints (Primary Key, Foreign Key, Check & Unique) | Beginner |
| 12 | How do you write a query that retrieves data from a table on a linked server? SQL Server › Linked Servers | SQL Server | Linked Servers | Beginner |
| 13 | What is a subquery in SQL Server, and how is it typically used within a larger query? SQL Server › Subqueries | SQL Server | Subqueries | Beginner |
| 14 | What is the difference between a correlated and a non correlated subquery? SQL Server › Subqueries | SQL Server | Subqueries | Beginner |
| 15 | What is a hash join, and how does SQL Server use it to combine two tables? SQL Server › Hash Indexes & Hash Join Operations | SQL Server | Hash Indexes & Hash Join Operations | Beginner |
| 16 | How do you convert a JSON array stored in a column into a relational table format that can be queried like normal rows? SQL Server › JSON Support in SQL Server | SQL Server | JSON Support in SQL Server | Intermediate |
| 17 | What is the difference between using EXISTS and IN when checking for the presence of related data with a subquery? SQL Server › Subqueries | SQL Server | Subqueries | Intermediate |
| 18 | How do you use a subquery within the SELECT list to calculate a related aggregate value alongside each row of the outer query? SQL Server › Subqueries | SQL Server | Subqueries | Intermediate |
| 19 | How do you use the query and nodes methods to work with repeating elements within an XML document, such as a list of items in an order? SQL Server › XML Data Type & Querying | SQL Server | XML Data Type & Querying | Intermediate |
| 20 | How do you design a schema to properly handle a many to many relationship between two entities, such as students and courses? SQL Server › Data Types & Schema Design | SQL Server | Data Types & Schema Design | Advanced |
| 21 | How does dynamic data masking behave differently when a masked column is used in a JOIN, WHERE clause, or exported through an application, compared to a simple SELECT query? SQL Server › Dynamic Data Masking | SQL Server | Dynamic Data Masking | Advanced |
| 22 | How would you use query hints to influence the optimizer's behavior when you have determined the default execution plan is genuinely suboptimal? SQL Server › Query Optimization & Plans | SQL Server | Query Optimization & Plans | Advanced |
| 23 | How would you rewrite a slow correlated subquery as an equivalent, potentially faster JOIN based query? SQL Server › Subqueries | SQL Server | Subqueries | Advanced |
| 24 | How does the SQL Server query optimizer typically handle and potentially transform a subquery internally when generating an execution plan? SQL Server › Subqueries | SQL Server | Subqueries | Advanced |