SQL Database Developer Interview Questions and Answers

I have extensive experience in SQL database development and programming languages.

• I have worked with SQL databases such as MySQL, Oracle, and SQL Server.

• I am proficient in writing complex SQL queries, stored procedures, and triggers.

• I have experience in database design, normalization, and performance optimization.

• I am familiar with programming languages like Java, Python, and C#.

• I have developed applications that interact with databases using JDBC, SQLAlchemy, and ADO.NET.

A database is a structured collection of data that is stored and accessed electronically.

• DBMS stands for Database Management System, which is a software that manages databases.

• RDBMS stands for Relational Database Management System, which organizes data into tables with rows and columns.

• Examples of RDBMS include MySQL, Oracle, and SQL Server.

An index is a data structure that improves the speed of data retrieval operations on a database table.

• Indexes can be created on one or more columns in a table.

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

• Indexes help in quickly locating data without having to scan the entire table.

• Example: Creating an index on the 'employee_id' column in a table of employee records.

Delete removes specific rows while truncate removes all rows from a table

• Delete is a DML command while truncate is a DDL command

• Delete can be rolled back while truncate cannot be rolled back

• Delete is slower than truncate as it logs each row deletion

• Delete can have a WHERE clause to specify which rows to delete while truncate cannot

• Example: DELETE FROM table_name WHERE column_name = value;

• Example: TRUNCATE TABLE table_name;

DBMS stands for Database Management System and RDBMS stands for Relational Database Management System.

• DBMS is a software system that allows users to define, create, maintain and control access to databases.

• RDBMS is a type of DBMS that stores data in the form of tables with rows and columns.

• RDBMS uses SQL (Structured Query Language) to manipulate data.

• Examples of popular RDBMS include MySQL, Oracle, and Microsoft SQL Server.

A self-join is when a table is joined with itself, typically to compare rows within the same table.

• Self-joins are used to compare rows within the same table by creating an alias for the table.

• They are commonly used to retrieve hierarchical data or compare related rows.

• Example: SELECT e1.employee_name, e2.manager_name FROM employees e1 JOIN employees e2 ON e1.manager_id = e2.employee_id

Tables are structures that store data in a database, while fields are columns within a table that hold specific pieces of information.

• Tables are like spreadsheets with rows and columns

• Fields are the columns in a table that hold specific types of data

• Examples: 'Employees' table with fields like 'Name', 'Age', 'Salary'