Sql-Interview

This is a post in the SQL Interview series. These aren’t trick or gotcha questions, they’re just questions designed to scope out a candidate’s knowledge around SQL Server and Azure SQL Database. Section: Development Level: Medium Question: When writing T-SQL code, you often need to replace NULL values. The core two functions provided are ISNULL and COALESCE. What is the difference between them? Answer: ISNULL only takes a single value to check and replaces it when NULL.

2025-02-15

This is a post in the SQL Interview series. These aren’t trick or gotcha questions, they’re just questions designed to scope out a candidate’s knowledge around SQL Server and Azure SQL Database. Section: Security Level: Intro Question: SQL Server can use both logins and users. What is the difference between them? Answer: A login provides access to the server, but not necessarily to any databases. A user is used to provide access to a database.

2025-02-11

This is a post in the SQL Interview series. These aren’t trick or gotcha questions, they’re just questions designed to scope out a candidate’s knowledge around SQL Server and Azure SQL Database. Section: Development Level: Medium Question: While developers don’t mind adding indexes to a database, most people are very nervous about ever removing them. Tools let us see whether or not an index is being used, but it’s useful to know why the index was added in the first place.

2025-02-07

This is a post in the SQL Interview series. These aren’t trick or gotcha questions, they’re just questions designed to scope out a candidate’s knowledge around SQL Server and Azure SQL Database. Section: Administration Level: Medium Question: You have two tables: dbo.Customers dbo.Orders The dbo.Orders table has a column CustomerID that is declared as a foreign key to the CustomerID column in the dbo.Customers table. In the dbo.Customers table, CustomerID is the primary key.

2025-02-06

This is a post in the SQL Interview series. These aren’t trick or gotcha questions, they’re just questions designed to scope out a candidate’s knowledge around SQL Server and Azure SQL Database. Section: Development Level: Medium Question: You see the following statement in a query that you are reviewing. What is the purpose of the NULLIF function in this statement? SELECT @a / NULLIF(@b, 0); What was the author trying to achieve?

2025-02-05

This is a post in the SQL Interview series. These aren’t trick or gotcha questions, they’re just questions designed to scope out a candidate’s knowledge around SQL Server and Azure SQL Database. Section: Development Level: Intro Question: I execute the following query: SELECT st.SalesTerritoryID AS [ID], st.SalesTerritoryName AS [Name], st.DateCreated FROM dbo.SalesTerritories AS st UNION SELECT p.ProductID AS [Product], p.[Description], p.DateCreated AS [StartDate] FROM dbo.Products AS p; What alias will be returned for the each column in the returned results?

2025-02-04

This is a post in the SQL Interview series. These aren’t trick or gotcha questions, they’re just questions designed to scope out a candidate’s knowledge around SQL Server and Azure SQL Database. Section: Security Level: Medium Question: User1 has CONNECT permission to a SQL Server and is a member of the db_datawriter role in the database Database1. User2 has CONNECT permission to the same SQL Server and is a member of the db_datareader role in the database Database1.

2025-01-31

This is a post in the SQL Interview series. These aren’t trick or gotcha questions, they’re just questions designed to scope out a candidate’s knowledge around SQL Server and Azure SQL Database. Section: Development Level: Medium Question: UNION and UNION ALL are commonly used to combine two sets of rows into a single set of rows. EXCEPT is another set operator. Can you explain what it does? Answer: EXCEPT is used to remove any rows in the first set of rows, if the same rows appear in the second set.

2021-04-29

This is a post in the SQL Interview series. These aren’t trick or gotcha questions, they’re just questions designed to scope out a candidate’s knowledge around SQL Server and Azure SQL Database. Section: Server Tuning Level: Advanced Question: SQL Server 2008 introduced a server option for optimize for adhoc workloads. Can you explain the problem that it is designed to solve, what most commonly causes the problem, and what impact this option has when you enable it?

2021-04-27

This is a post in the SQL Interview series. These aren’t trick or gotcha questions, they’re just questions designed to scope out a candidate’s knowledge around SQL Server and Azure SQL Database. Section: Development Level: Intro Question: Consider the following code: SELECT CustomerID, CustomerName FROM Sales.Customers WHERE BusinessCategory = 'Cafe' UNION SELECT CustomerID, CustomerName FROM Sales.Customers WHERE City = 'Toronto'; A: What would be the difference in results if the query was changed to use a UNION ALL instead of the UNION?

2021-04-22