Database Interview Questions

38 real Database questions asked in live technical interviews — each with a model answer. Updated weekly.

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If we join two tables with an inner join, how many records will result? How many combinations will be produced?🟡 Medium · Conceptual · Asked 12×What is ACID design?🟢 Easy · Conceptual · Asked 3×Write an SQL query to select the top 10 users by order.🟢 Easy · Coding · Asked 1×Which database or storage solution would you use in a scenario where customers' phone numbers are changing frequently, such as in a telecommunications company?🟡 Medium · Conceptual · Asked 1×What is the difference between clustering and non-clustering indexes?🟡 Medium · Conceptual · Asked 1×Are you aware of clustering?🟢 Easy · Conceptual · Asked 1×What basic SQL query optimization techniques do you use?🟡 Medium · Conceptual · Asked 1×Can you explain transaction isolation levels?🟢 Easy · Conceptual · Asked 1×Can you explain clustered and non-clustered indexes and how they are created?🟢 Easy · Conceptual · Asked 1×What is the typical flow from a database to a data lake, and what is the final step in the data pipeline?🟡 Medium · Conceptual · Asked 1×We are talking about a Databricks pipeline. Which pipeline did you develop, and which database did you use?🟡 Medium · Conceptual · Asked 1×Which database service can be used to build a pipeline that uses native PySpark code?🟡 Medium · Conceptual · Asked 1×Can you write a query to determine whether a table is permanent or temporary?🟡 Medium · Coding · Asked 1×In case multiple users report blocking while updating the same table, what approach would you take to minimize contention?🟡 Medium · Conceptual · Asked 1×What is Azure SQL?🟢 Easy · Conceptual · Asked 1×Can you explain how you optimize SQL code when the client does not want to disturb existing data?🟡 Medium · Conceptual · Asked 1×Can you tell how you would handle a schema violation?🟡 Medium · Conceptual · Asked 1×How are data warehouses different from databases? For example, DynamoDB is a database, Snowflake is a data warehouse. What is the main purpose of a data warehouse?🟡 Medium · Conceptual · Asked 1×Write an SQL query that returns the employee name and the manager name for each employee.🟢 Easy · Coding · Asked 1×How can you display only two columns, email and WhatsApp, in a data table?🟢 Easy · Conceptual · Asked 1×How do you secure specific columns in a BI data table?🟡 Medium · Conceptual · Asked 1×Does the employee table have columns employee id and employee name?🟢 Easy · Conceptual · Asked 1×What are the types of data models?🟢 Easy · Conceptual · Asked 1×Write a SQL query that can view attendance for approximately 100 employees in the system.🟡 Medium · Coding · Asked 1×How can we retrieve the size of a table in Redshift, for example when the table is about one gigabyte, and what options should we consider?🟡 Medium · Conceptual · Asked 1×The table is queried by ID, but the ID is modified frequently.🟡 Medium · Conceptual · Asked 1×How would you modify columns such as modify date, creator date, quantity, order number, and SKU, and optionally drop a column named 'chat'?🟡 Medium · Conceptual · Asked 1×Define the relationship dependencies between tasks.🟡 Medium · Conceptual · Asked 1×Can you again tell me what the execution plan for a query is?🟡 Medium · Conceptual · Asked 1×What is the number of rows in the customer table?🟢 Easy · Conceptual · Asked 1×What is the total number of customers?🟢 Easy · Conceptual · Asked 1×What is the count of rows in the stats table?🟢 Easy · Conceptual · Asked 1×How can we return two rows in the result set while only referencing one row?🟡 Medium · Conceptual · Asked 1×Which row will be returned in the result set?🟢 Easy · Conceptual · Asked 1×Given the following tables: TableA: | id | |----| | 1 | | 1 | | 2 | | 3 | | 4 | TableB: | id | |----| | 1 | | 2 | | 3 | | 4 | How many records would result from an inner join and from a left join on the id column?🟢 Easy · Conceptual · Asked 1×Can you tell what a primary key is?🟢 Easy · Conceptual · Asked 1×Are you confident with SQL? Would you rate yourself out of five?🟢 Easy · Behavioral · Asked 1×Write Python Django code to create an API that fetches a value from a query parameter and inserts this value into a database.🟡 Medium · Coding · Asked 1×

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