database architect Interview Questions and Answers

1. What is a database?

   • Answer: A database is a structured set of data organized and accessed electronically from a computer system. It's designed for efficient storage, retrieval, modification, and deletion of data. Different types of databases exist, including relational, NoSQL, and graph databases, each with its strengths and weaknesses.

2. Explain the difference between OLTP and OLAP databases.

   • Answer: OLTP (Online Transaction Processing) databases are optimized for handling a high volume of short transactions, like those in online banking or e-commerce. OLAP (Online Analytical Processing) databases are optimized for analytical queries and reporting, often using large datasets to identify trends and patterns. They differ in design, data organization, and query processing techniques.

3. What is normalization and why is it important?

   • Answer: Normalization is a database design process that reduces data redundancy and improves data integrity. It involves organizing data into tables in such a way that database integrity constraints properly enforce dependencies. This minimizes data anomalies (insertion, update, and deletion anomalies) and improves the efficiency and scalability of the database.

4. Explain ACID properties.

   • Answer: ACID properties are crucial for ensuring data integrity in database transactions: Atomicity (all parts of a transaction succeed or none do), Consistency (a transaction maintains database integrity), Isolation (concurrent transactions are isolated from each other), and Durability (committed transactions persist even in case of failures).

5. What are indexes and how do they work?

   • Answer: Indexes are data structures that improve the speed of data retrieval operations on a database table. They work by creating a separate lookup table that contains a subset of columns and their row pointers, allowing the database to quickly locate rows that match a specific search criterion without scanning the entire table.

6. What is a database trigger?

   • Answer: A database trigger is a procedural code that automatically executes in response to certain events on a particular table or view in a database. Triggers can be used to enforce data integrity constraints, audit data changes, or perform other automated tasks.

7. Explain the difference between clustered and non-clustered indexes.

   • Answer: A clustered index determines the physical order of data rows in a table. There can only be one clustered index per table. A non-clustered index is a separate structure that points to the data rows; a table can have multiple non-clustered indexes. Clustered indexes are generally faster for retrieving data based on the indexed columns.

8. What is a stored procedure?

   • Answer: A stored procedure is a pre-compiled SQL code block that can be stored and executed in the database. They offer several advantages, including improved performance (due to pre-compilation), enhanced security (by controlling access), and code reusability.

9. What is a view in a database?

   • Answer: A view is a virtual table based on the result-set of an SQL statement. It doesn't store data itself but provides a customized way to access data from one or more underlying tables. Views can simplify data access, enhance security by restricting access to specific columns, and provide a consistent interface for data.

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