20+ SQL Server Developer Interview Questions and Answers

Generate unique match pairs from a single-column team table using SQL.

• Use a self-join on the TEAM table to create pairs.

• Ensure to filter out duplicate matches by using a condition like t1.teamname < t2.teamname.

• Example SQL query: SELECT t1.teamname AS Team1, t2.teamname AS Team2 FROM TEAM t1, TEAM t2 WHERE t1.teamname < t2.teamname;

WHERE clause is used to filter rows before grouping, HAVING clause is used to filter groups after grouping.

• WHERE clause is used with SELECT, UPDATE, DELETE statements to filter rows based on a condition.

• HAVING clause is used with SELECT statement to filter groups based on a condition.

• WHERE clause is applied before the data is grouped, HAVING clause is applied after the data is grouped.

• Example: SELECT * FROM table_name WHERE column_name = 'value';

• Example: SELECT column_name, C...read more

Steps to create a data flow task for a publication software involve planning, designing, and implementing the data flow.

• Identify the source and destination of the data flow, e.g., SQL Server to a reporting database.

• Define the transformation logic needed, such as data cleansing or aggregation.

• Use ETL tools like SSIS to design the data flow task visually.

• Test the data flow task with sample data to ensure accuracy.

• Schedule the task for regular execution using SQL Server Agent.

Different types of SQL joins with given data sets a and b.

• Inner join: Returns rows where there is a match in both tables (1,1)

• Left join: Returns all rows from the left table and the matched rows from the right table (1,1,1,2,2)

• Right join: Returns all rows from the right table and the matched rows from the left table (1,1,2,4)

• Cross join: Returns the Cartesian product of the two tables (1,1,1,1,1,2,1,4,1,1,2,1,2,2,1,4,2,1,2,2,2,2,4,3,1,1,3,1,2,3,1,4,3,1,1,3,2,2,3,2,4,3,1,2,3,2,...read more

Effective transaction management ensures data integrity and consistency in SQL Server through proper use of ACID properties.

• Use BEGIN TRANSACTION to start a transaction and ensure all operations are treated as a single unit.

• Implement COMMIT to save changes if all operations succeed, e.g., COMMIT TRANSACTION;

• Use ROLLBACK to undo changes if an error occurs, e.g., ROLLBACK TRANSACTION;

• Utilize transaction isolation levels (e.g., READ COMMITTED) to control concurrency and prevent ...read more

Indexes are data structures that improve the speed of data retrieval operations in a database.

• Indexes are used to quickly locate data without having to search every row in a database table.

• Types of indexes include clustered, non-clustered, unique, and composite indexes.

• Clustered indexes determine the physical order of data in a table, while non-clustered indexes store a separate copy of the indexed columns.

• Unique indexes ensure that no two rows have the same values in the ind...read more

Functions return a value, while stored procedures do not. Functions can be used in SELECT statements, stored procedures cannot.

• Functions return a single value, while stored procedures can return multiple values or none at all.

• Functions can be used in SELECT statements to return a value, while stored procedures cannot be used in this way.

• Functions can be called from within stored procedures, but stored procedures cannot be called from within functions.

Primary key uniquely identifies each record in a table, while Unique key allows only one instance of a value in a column.

• Primary key does not allow NULL values, while Unique key allows one NULL value.

• Primary key automatically creates a clustered index, while Unique key creates a non-clustered index by default.

• Primary key can be referenced by foreign keys, while Unique key cannot be referenced by foreign keys.

row_number, rank, dense_rank are window functions in SQL used to assign a unique number to each row based on specified criteria.

• row_number() assigns a unique sequential integer starting from 1 to each row in the result set

• rank() assigns a unique rank to each row based on the specified ordering criteria, with gaps in ranking for ties

• dense_rank() assigns a unique rank to each row based on the specified ordering criteria, with no gaps in ranking for ties

Integrity constraints are rules that ensure data integrity and consistency in a database.

• Integrity constraints are used to enforce business rules and maintain data accuracy.

• Common types of integrity constraints include primary key, foreign key, unique key, and check constraints.

• For example, a primary key constraint ensures that each row in a table is uniquely identified by a specific column or combination of columns.

DML commands are Data Manipulation Language commands used to manage data in a database.

• DML commands include INSERT, UPDATE, DELETE, and SELECT.

• INSERT is used to add new rows of data into a table.

• UPDATE is used to modify existing data in a table.

• DELETE is used to remove rows of data from a table.

• SELECT is used to retrieve data from a database.

Types of joins in SQL are Inner Join, Left Join, Right Join, and Full Join.

• Inner Join: Returns rows when there is a match in both tables.

• Left Join: Returns all rows from the left table and the matched rows from the right table.

• Right Join: Returns all rows from the right table and the matched rows from the left table.

• Full Join: Returns rows when there is a match in one of the tables.

Execution plan is a roadmap that SQL Server uses to execute a query, showing the steps taken to retrieve data.

• Execution plan is generated by the query optimizer to determine the most efficient way to execute a query.

• It shows the order in which tables are accessed, joins are performed, and filters are applied.

• Execution plan can be viewed using tools like SQL Server Management Studio or by using the EXPLAIN statement in some databases.

A stored procedure is a precompiled collection of SQL statements that can be executed by calling the procedure name.

• Stored procedures can accept input parameters and return output parameters.

• They can be used to encapsulate complex logic and improve performance by reducing network traffic.

• Stored procedures are stored in the database and can be reused by multiple applications or users.

• Example: CREATE PROCEDURE GetEmployeeDetails AS SELECT * FROM Employees WHERE Department = 'IT...read more

SQL commands are instructions used to interact with a database management system to perform tasks such as querying, updating, and managing data.

• SQL commands are used to perform various operations on a database, such as selecting data with SELECT, inserting data with INSERT, updating data with UPDATE, and deleting data with DELETE.

• Other common SQL commands include CREATE TABLE for creating tables, ALTER TABLE for modifying tables, and DROP TABLE for deleting tables.

• SQL command...read more

A trigger is a special type of stored procedure that automatically executes when certain events occur in a database.

• Triggers can be used to enforce business rules, maintain referential integrity, and automate repetitive tasks.

• Examples of trigger events include INSERT, UPDATE, and DELETE operations on a table.

• Triggers can be defined to execute before or after the triggering event.

Join is used to combine rows from two or more tables based on a related column between them.

• Join is used to retrieve data from multiple tables in a single query.

• Types of joins include Inner Join, Left Join, Right Join, and Full Outer Join.

• Join conditions are specified using the ON keyword.

• Example: SELECT * FROM table1 INNER JOIN table2 ON table1.column = table2.column;

• Joins can also be nested to combine more than two tables.

Different types of joins in SQL include inner join, left join, right join, and full outer join.

• Inner join: Returns rows when there is a match in both tables.

• Left join: Returns all rows from the left table and the matched rows from the right table.

• Right join: Returns all rows from the right table and the matched rows from the left table.

• Full outer join: Returns rows when there is a match in either table.

A join in SQL combines rows from two or more tables based on a related column.

• Types of joins: INNER JOIN, LEFT JOIN, RIGHT JOIN, FULL OUTER JOIN.

• INNER JOIN returns records with matching values in both tables.

• LEFT JOIN returns all records from the left table and matched records from the right table.

• RIGHT JOIN returns all records from the right table and matched records from the left table.

• FULL OUTER JOIN returns all records when there is a match in either left or right table.

• E...read more

The key of reusability in SQL Server development is creating modular, efficient code that can be easily adapted and reused.

• Use stored procedures and functions to encapsulate logic for reuse.

• Implement common table expressions (CTEs) to simplify complex queries that are used frequently.

• Utilize user-defined data types and user-defined functions to standardize data processing tasks.

• Leverage views to encapsulate complex queries and make them reusable across multiple queries or rep...read more