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Question-1. What is T-SQL?
Answer-1: T-SQL (Transact-SQL) is an extension of SQL used in Microsoft SQL Server for procedural programming, error handling, and transaction control.
Question-2. How is T-SQL different from standard SQL?
Answer-2: T-SQL includes control-of-flow, error handling, variables, stored procedures, functions, and transactions, which are not present in standard SQL.
Question-3. What is the difference between CHAR and VARCHAR in T-SQL?
Answer-3: CHAR has a fixed length, while VARCHAR has a variable length and saves space.
Question-4. How do you declare a variable in T-SQL?
Answer-4: DECLARE @variableName INT;
Question-5. How do you assign a value to a variable in T-SQL?
Answer-5: SET @variableName = 100; or SELECT @variableName = column FROM Table;
Question-6. What is a stored procedure in T-SQL?
Answer-6: A precompiled set of SQL statements that can be executed multiple times.
Question-7. How do you create a stored procedure in T-SQL?
Answer-7: CREATE PROCEDURE ProcName AS BEGIN SELECT * FROM Table END;
Question-8. What is the difference between DELETE and TRUNCATE?
Answer-8: DELETE removes rows one by one and logs them, while TRUNCATE removes all rows instantly without logging.
Question-9. What is a trigger in T-SQL?
Answer-9: A special procedure that automatically executes in response to an INSERT, UPDATE, or DELETE event on a table.
Question-10. How do you create a trigger in T-SQL?
Answer-10: CREATE TRIGGER trgName ON Table AFTER INSERT AS BEGIN PRINT 'Insert Trigger Fired' END;
Question-11. What are transactions in T-SQL?
Answer-11: A sequence of operations that are executed as a single unit (Atomicity, Consistency, Isolation, Durability - ACID).
Question-12. How do you start a transaction in T-SQL?
Answer-12: BEGIN TRANSACTION;
Question-13. How do you commit a transaction in T-SQL?
Answer-13: COMMIT TRANSACTION;
Question-14. How do you roll back a transaction in T-SQL?
Answer-14: ROLLBACK TRANSACTION;
Question-15. What is the difference between INNER JOIN and OUTER JOIN?
Answer-15: INNER JOIN returns only matching records, while OUTER JOIN returns all records with NULLs for non-matching rows.
Question-16. How do you use LEFT JOIN in T-SQL?
Answer-16: SELECT * FROM TableA LEFT JOIN TableB ON TableA.ID = TableB.ID;
Question-17. What is a CASE statement in T-SQL?
Answer-17: A conditional expression used to implement IF-ELSE logic inside SQL queries.
Question-18. How do you use a CASE statement in T-SQL?
Answer-18: SELECT Name, CASE WHEN Age > 18 THEN 'Adult' ELSE 'Minor' END AS Category FROM Users;
Question-19. What is COALESCE() in T-SQL?
Answer-19: A function that returns the first non-null value from a list.
Question-20. How do you find duplicate records in a table?
Answer-20: SELECT Column, COUNT(*) FROM Table GROUP BY Column HAVING COUNT(*) > 1;
Question-21. What is the difference between RANK(), DENSE_RANK(), and ROW_NUMBER()?
Answer-21: RANK() leaves gaps in ranking, DENSE_RANK() does not leave gaps, and ROW_NUMBER() provides unique numbers.
Question-22. How do you find the second highest salary using T-SQL?
Answer-22: SELECT MAX(Salary) FROM Employees WHERE Salary < (SELECT MAX(Salary) FROM Employees);
Question-23. What is a Common Table Expression (CTE) in T-SQL?
Answer-23: A temporary result set that can be referenced within a SELECT, INSERT, UPDATE, or DELETE query.
Question-24. How do you create a CTE in T-SQL?
Answer-24: WITH CTE AS (SELECT * FROM Table) SELECT * FROM CTE;
Question-25. What is a temporary table in T-SQL?
Answer-25: A table stored in tempdb and used within a session (#TempTable).
Question-26. What is a table variable in T-SQL?
Answer-26: A variable (@TableVariable) that stores a temporary result set like a table but exists only within a batch.
Question-27. How do you create a temporary table in T-SQL?
Answer-27: CREATE TABLE #TempTable (ID INT, Name VARCHAR(50));
Question-28. How do you create a table variable in T-SQL?
Answer-28: DECLARE @TableVar TABLE (ID INT, Name VARCHAR(50));
Question-29. What is the difference between HAVING and WHERE?
Answer-29: WHERE filters before aggregation, while HAVING filters after aggregation.
Question-30. What is an index in T-SQL?
Answer-30: A structure that improves query performance by reducing scan time.
Question-31. What are the types of indexes in T-SQL?
Answer-31: Clustered, Non-clustered, Unique, Full-text, Columnstore.
Question-32. How do you create an index in T-SQL?
Answer-32: CREATE INDEX idx_name ON Table(Column);
Question-33. What is a primary key in T-SQL?
Answer-33: A unique identifier for a table row (cannot contain NULL values).
Question-34. What is a foreign key in T-SQL?
Answer-34: A field in a table that references a primary key in another table.
Question-35. How do you add a primary key to a table?
Answer-35: ALTER TABLE Table ADD PRIMARY KEY (Column);
Question-36. How do you add a foreign key in T-SQL?
Answer-36: ALTER TABLE ChildTable ADD FOREIGN KEY (Column) REFERENCES ParentTable(Column);
Question-37. What is the IDENTITY property in T-SQL?
Answer-37: It generates auto-incrementing numbers for a column.
Question-38. How do you insert data into an identity column?
Answer-38: INSERT INTO Table (Name) VALUES ('John'); (ID auto-increments).
Question-39. How do you retrieve the last inserted identity value?
Answer-39: SELECT SCOPE_IDENTITY();
Question-40. How do you update data in T-SQL?
Answer-40: UPDATE Table SET Column = Value WHERE Condition;
Question-41. How do you delete a row in T-SQL?
Answer-41: DELETE FROM Table WHERE Condition;
Question-42. How do you use EXISTS in T-SQL?
Answer-42: SELECT * FROM Table WHERE EXISTS (SELECT 1 FROM OtherTable WHERE ID = Table.ID);
Question-43. What is the purpose of TRY...CATCH in T-SQL?
Answer-43: To handle runtime errors inside stored procedures.
Question-44. How do you implement TRY...CATCH in T-SQL?
Answer-44: BEGIN TRY -- SQL Code END TRY BEGIN CATCH -- Error Handling END CATCH;
Question-45. How do you fetch the first 10 records in T-SQL?
Answer-45: SELECT TOP 10 * FROM Table;
Question-46. How do you paginate results in T-SQL?
Answer-46: SELECT * FROM Table ORDER BY ID OFFSET 10 ROWS FETCH NEXT 10 ROWS ONLY;
Question-47. What is MERGE in T-SQL?
Answer-47: It allows INSERT, UPDATE, and DELETE in one statement based on condition.
Question-48. How do you use MERGE in T-SQL?
Answer-48: MERGE INTO TargetTable USING SourceTable ON Condition WHEN MATCHED THEN UPDATE SET Column = Value WHEN NOT MATCHED THEN INSERT (Column) VALUES (Value);
Question-49. How do you check SQL Server version using T-SQL?
Answer-49: SELECT @@VERSION;
Question-50. What is DBCC CHECKDB used for?
Answer-50: It checks database integrity and consistency.
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