Top 10 SQL Interview Questions & Answers
SQL is a programming language. Programmers often use it to manage data in the relational database system. After its first appearance in 1974, it become one of the most popular programming system. We can claim that because people over the world are using it more than other languages.
Because of that there are hundreds of conferences and interviews about it. This topic is so popular between experts and users, so we prepare top 10 SQL interview questions and answers for you. We hope that this information could help you to understand something or find something interesting.
- Question: what SQL is? Very often people couldn`t give the right answer so we want to correct that mistake. Answer: SQL (Structured Query Language) is a tool. User could use it to create database to support and application.
- Question: what are transactions and its controls?Answer: transaction determines like a sequence task, which is performed on databases in a logical manner to get the necessary result. We can name four important transaction controls, which are used most: COMMIT, ROLLBACK, SET TRANSACTION, SAVEPOINT.
- Question: does the transactions have properties and what could they give to users? This is one of the most popular rdbms interview questions on this topic. Answer: the properties of transactions, also known as ACID properties, could say whether every transaction is performed or check if changes of one transaction are not reflected on the other transactions.
- Question: what is RDBMS? RDBMS interview questions are also in demand between journalists and typical users. Answer? RDBMS is an abbreviature and means next: Relational Database Management System. With it user can have relation inside the database.
- Question: Can you explain the DDL commands and where is the difference between them? Answer: DDL (Data Definition Language) is needed when we must define or alter the structure of the database. We have the list of commands and their explanation. CREATE – to create a table in to the database, DROP – to drop the table from the database, RENAME – system will change the name of the database, TRUNCATE – this command will delete every record inside the database, but not it`s structure, ALTER – to alter all database structure.
- Question: can you explain the DML commands? Answer: the DML means Data Manipulation Language. It also has some commands which could be use for some operations. There is no need to make an explanation because here we have simple commands like delete, insert, select, copy and others.
These questions are the most popular while discussing the topic of SQL. We also have questions like “What is a table?”, “What is field in a table?” or “Can you tell us about recording in a table?”. However, they are very simple and you can easily find the answers while reading the database normalization interview.