HCLTech SQL Developer Interview Questions, Process, and Tips

Q1. Difference between keys and indexes in sql
Ans. 
Keys uniquely identify records, while indexes improve query performance by speeding up data retrieval.
• A primary key is a unique identifier for a record in a table, e.g., 'user_id' in a 'users' table.

• A foreign key establishes a relationship between two tables, e.g., 'order_id' in 'orders' referencing 'user_id' in 'users'.

• Indexes are data structures that improve the speed of data retrieval operations on a database table,...read more
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Q2. Is keys creates a index ?
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Q3. What r the types of index and keys?
Ans. 
Indexes and keys are essential database structures that enhance data retrieval and enforce data integrity.
• Primary Key: Uniquely identifies each record in a table. Example: 'user_id' in a 'users' table.

• Foreign Key: Establishes a relationship between two tables. Example: 'user_id' in 'orders' table referencing 'users'.

• Unique Key: Ensures all values in a column are unique. Example: 'email' in a 'users' table.

• Composite Key...read more
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Q4. Difference between identity and sequenceNo with more details?
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Identity columns auto-generate values for new rows, while sequences are independent objects for generating unique numbers.
• Identity: Automatically generates a unique value for each new row in a table.

• Example: In SQL Server, you can define a column as 'IDENTITY(1,1)' to start at 1 and increment by 1.

• Sequence: A separate database object that generates a sequence of numeric values.

• Example: In Oracle, you can create a seque...read more
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Q5. Difference between truncate and drop with more details. eg: 'A' table have a identity column with 10 rows. if I tried to delete or truncate a 2nd row, then what will be next value of identity column? (Plea...read more
Ans. 
Truncate removes all rows and resets identity, while delete removes specific rows without resetting identity.
• TRUNCATE TABLE removes all rows from a table and resets any identity columns to their seed value.

• DELETE FROM table_name removes specific rows based on a condition but does not reset identity columns.

• Example: If 'A' table has 10 rows with an identity column starting at 1, truncating will reset the next identity v...read more
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Q6. What is compile and recompile in sql?
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Compilation in SQL refers to the process of converting SQL code into an executable form, while recompilation occurs when changes are made.
• Compilation occurs when a SQL statement is first executed, creating an execution plan.

• Recompilation happens when the underlying data or schema changes, requiring a new execution plan.

• Example of recompilation: Changing a table structure (e.g., adding a column) may trigger recompilatio...read more
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Q7. What is execution plan?
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An execution plan is a roadmap that outlines how a SQL query will be executed by the database engine.
• It shows the steps the database will take to execute a query, including joins, scans, and sorts.

• Execution plans can be visualized using tools like SQL Server Management Studio or EXPLAIN in PostgreSQL.

• They help identify performance bottlenecks by showing which operations are most costly.

• Example: A query that joins two t...read more
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Q8. Uses of storeprocedures? (Eg: Execution plan use)
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Q9. Sql server architecture basic?
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Q10. Can we crud operation inside a function or view?
Ans. 
CRUD operations are not allowed inside functions or views in SQL due to side effects and consistency issues.
• Functions in SQL are meant to return values and cannot perform data modification (INSERT, UPDATE, DELETE).

• Views are virtual tables and are used to present data; they do not support direct data manipulation.

• Using a function to perform CRUD can lead to unpredictable results and violate the principle of function pur...read more
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Q11. Can we call a procedure from a function?
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Q12. Difference between table variable and temp table with example?
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Q13. Query writing with joins and group by with having clause , where clause?
Ans. 
Understanding SQL joins, group by, having, and where clauses for effective data querying.
• Joins combine rows from two or more tables based on a related column. Example: SELECT * FROM table1 JOIN table2 ON table1.id = table2.id;

• GROUP BY aggregates data across specified columns. Example: SELECT department, COUNT(*) FROM employees GROUP BY department;

• HAVING filters groups created by GROUP BY. Example: SELECT department, CO...read more
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Q14. Difference between where clause and having clause
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Q15. Type of functions and detailed explanation
Ans. 
SQL functions are categorized into scalar, aggregate, and window functions, each serving distinct purposes in data manipulation.
• Scalar Functions: Operate on a single value and return a single value. Example: UPPER('abc') returns 'ABC'.

• Aggregate Functions: Operate on a set of values and return a single summary value. Example: COUNT(*) counts the number of rows.

• Window Functions: Perform calculations across a set of table...read more
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Q16. What is cursors? Create a cursor ( just to check whether u know write a cursor query) Alternate way to create a cursor(Answer is while loop)
Ans. 
Cursors are database objects used to retrieve, manipulate, and navigate through a result set row by row.
• Cursors allow for row-by-row processing of SQL results.

• Types of cursors: implicit and explicit.

• Example of creating an explicit cursor: DECLARE cursor_name CURSOR FOR SELECT column_name FROM table_name;

• To fetch data from a cursor: FETCH cursor_name INTO variable_name;

• An alternate way to process rows is using a WHILE
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Q1. Tell me about your self
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I am an experienced SQL Developer with a strong background in database management and query optimization.
• Experienced SQL Developer

• Strong background in database management

• Expertise in query optimization
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Q2. Why choose this company
Ans. 
This company offers a collaborative work environment, cutting-edge technology, and opportunities for professional growth.
• Collaborative work environment: The company values teamwork and encourages collaboration among employees.

• Cutting-edge technology: The company stays up-to-date with the latest advancements in SQL development.

• Opportunities for professional growth: The company provides training programs and career devel...read more
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Basic concepts of aptitude and reasoning

Q1. They mostly ask from your resume
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Q2. Sql Quires on Joins, Stored procedures.
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Q1. Basic questions like your additional achievements if any, salary expectations.
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