SQL Interview Questions And Answers
It is a standard language for Relational Database System. It enables a user to create, read, update and delete relational databases and tables. SQL allows users to query the database in a number of ways, using English-like statements.
SQL is a greater tool with web languages such as PHP, Python, Java, ASP et cetera to build dynamic web applications. SQL is a very powerful and diverse database language use to storing data into databases. SQL is loosely typed language so you can learn easily sql interview questions and answers .
Before starting SQL, there are some important points to keep in mind.
1. RDBMS: stands for Relational Database Management System.
2. Data Integrity : Store data only once and avoiding data duplication.
3. SQL Constraints [ sql interview questions and answers ] : Constraints are the rules which are apply to table columns to store valid data and prevents the user to storing/entering invalid data into table columns.
4. Better security : Assign grant or privilege to a individual User. Using this grant user can store confidential data into table by using username or password.
5. Database Normalization [ sql interview questions and answers ] : Database normalization is the process to store database data very efficiently. No need to store same data more then one time and reduce the Data redundancy.
SQL Process [ sql interview questions and answers ] :
When an SQL command is executing for any RDBMS, then the system figure out the best way to carry out the request and the SQL engine determines that how to interpret the task sql interview questions and answers .
In the process, various components are included. These components can be optimization Engine, Query engine, Query dispatcher, classic, etc. All the non-SQL queries are handled by the classic query engine, but SQL query engine won’t handle logical files.
SQL follows the following rules [ sql interview questions and answers ] :
1. Statements of SQL are dependent on text lines. We can use a single SQL statement on one or multiple text line.
2. Using the SQL statements, you can perform most of the actions in a database.
3. Structure query language is not case sensitive. Generally, keywords of SQL are written in uppercase.
4. SQL depends on tuple relational calculus and relational algebra.
Features of SQL:
SQL contains of some important features and they are:
1. Data Manipulation Language (DML): Data Manipulation Language contains commands used to manipulate the data.
The commands are sql interview questions and answers :
insert: This command is generally used after the create command to insert a set of values into the table.
delete: A command used to delete particular tuples or rows or cardinality from the table.
update: It updates the tupples in a table.
2. Triggers: Triggers are actions performed when certain conditions are met on the data.
A trigger contains of three parts.
sql interview questions and answers
(i) event – The change in the database that activates the trigger is event.
(ii) condition – A query or test that is run when the trigger is activated.
(iii) action – A procedure that is executed when trigger is activated and the condition met is true.
3. Data Definition language (DDL): It contains of commands which defines the data.
The commands are:
create: It is used to create a table.
sql interview questions and answers
drop: It is used to delete the table including all the attributes.
alter: alter is a reserve word which modifies the structure of the table.
rename: A table name can be changed using the reserver ‘rename’
4. Security and authentication: SQL provides a mechanism to control the database meaning it makes sure that only the particular details of the database is to be shown the user and the original database is secured by DBMS.
5. Client server execution and remote database access: Client server technology maintains a many to one relationship of clients(many) and server(one). We have commands in SQL that control how a client application can access the database over a network. sql interview questions and answers
6. Embedded SQL: SQL provides the feature of embedding host languages such as C, COBOL, Java for query from their language at runtime.
7. Transaction Control Language: Transactions are an important element of DBMS and to control the transactions, TCL is used which has commands like commit, rollback and savepoint. sql interview questions and answers
commit: It saves the database at any point whenever database is consistent.
rollback: It rollbacks/undo to the previous point of the transaction.
savepoint: It goes back to the previous transaction without going back to the entire transaction.
8. Advanced SQL: The current features include OOP ones like recursive queries, decision-supporting queries and also query supporting areas like data mining, spatial data and XML ( sql interview questions and answers ).
Need of SQL [ sql interview questions and answers ] :
• It is widely used in the Business Intelligence tool.
• It is one of the demanding industrial skills.
• Data Manipulation and data testing are done through SQL.
• Data Science tools depend highly on SQL. Big data tools such as Spark, Impala are dependent on SQL.
Advantages of SQL [ sql interview questions and answers ] :
SQL has many advantages which makes it popular and highly demanded. It is a reliable and efficient language used for communicating with the database.
Some advantages of SQL are as follows:
No Coding Skills: For data retrieval, large number of lines of code is not required. All basic keywords such as SELECT, INSERT INTO, UPDATE, etc are used and also the syntactical rules are not complex in SQL, which makes it a user-friendly language.
Faster Query Processing: Large amount of data is retrieved quickly and efficiently. Operations like Insertion, deletion, manipulation of data is also done in almost no time. sql interview questions and answers
Portable: It can be used in programs in PCs, server, laptops independent of any platform. Also, it can be embedded with other applications as per need/requirement/use.
Interactive Language: Easy to learn and understand, answers to complex queries can be received in seconds.
Standardized Language: Due to documentation and long establishment over years, it provides a uniform platform worldwide to all its users.
Applications of SQL :
• It is used to deal with analytical queries to analyze the data and get instincts from it.
• Modification/Manipulation of data and database table such as Insertion, Deletion and Updation.
• SQL is used by developers and DBAs (Database Administrators) in writing Data Integration Scripts.
• For retrieving an Information.
SQL Process Flow [ sql interview questions and answers ]:
When you execute SQL query come to a SQL Server. SQL Server work is managing database, load balancing, transaction management etc. SQL server call to a actual physical database table and return the result. This process is take small bit of time and depend of query and SQL server load.
SQL stored procedures are compiled once and stored in executable form, so procedure calls are efficient. Today almost all RDBMS(MySql, Oracle, Infomix, Sybase, MS Access) use SQL as the standard database query language. SQL is used to perform all types of data operations in RDBMS.
Frequently Asked Questions:
What is SQL introduction?
What is the concept of SQL?
What is SQL and its purpose?
What is SQL and its types?
Here you will find answers to questions on everything from the features you can expect, all of which makes up part of the SQL training from Asha24.