What Is SQL?
SQL is a domain-specific language. It is used in application development language to enable a programmer to work with the data. The data is stored in a relational database. To manage this data, we have relational database management systems like SQL Server, MySQL, MS Access, etc. that use SQL as a standard database language.
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This introduction to SQL tutorial will give you a quick overview on:
What does SQL stand for?
A common question is “what is the full form of sql”. SQL stands for Structured Query Language. The original name of the language was SEQUEL, created for IBM System R research database in 1970, but due to copyright issues, they changed the name to SQL.
What Is Data?
Data is distinct pieces of information, which can be facts, figures, or details that are stored in or used by a computer.
What Is a Database?
A database is a well-organized collection of data that is stored in an electronic format. To be more specific, a SQL database is an electronic system that allows to easily access, manipulate, and update the data.
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What Is a Database Management System?
Consider a School SQL Database which has a record of the present students and the previously studied students in the Student Details table. Similarly, it may contain Faculty Details, Management Details, Staff Details, and many more depending on the school’s requirement. As the data is in huge amounts, to manage it we need a database management system.
Almost all modern databases are managed by a Database Management System (DBMS). Basically, it is a system software used for creating data in a systematic way and managing databases.
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How Does SQL Database manage Data?
DBMS provides, for both users and programmers, a fundamental way to create, retrieve, update, and manage data.
Consider a scenario where a student XYZ wants to change his address. The DBMS searches the details of XYZ in the table ‘Student Details’ from the database ‘School Database’ and displays it for the user, and then the user edits it.
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Now, we have a clear picture of a database and its managing system. Let’s move on.
Types of Database Architecture
We have two types of database architecture:
- File Server
- Client Server
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File Server Architecture
In the file server architecture, files are located on the local system. It is useful for sharing information across a network. The client sends a request for a file over the network, and the file server forwards the file to the client. This is considered to be the most primitive type of data service used for exchanging information over a network. The file server provides access to remote server processors too.
Here is an example to understand the implementation of the file server.
Suppose, you have an Excel file and one of your friends requests you to send that file for some information. So, you send a copy to your friend. Now when you make any changes in your original Excel file, those changes would not be reflected in the file which is with your friend.
In this example, you are a file server and your friend is the device requesting the information. We can conclude on the file server architecture by quoting that the server acts as a sorting device and only one person at a time can have access to it.
Client Server Architecture
In the client server architecture, the database is the server and any application that uses the data is a client.
Here is an example to explain the working of this server. Consider three OLE DB components or client systems accessing the database at the same time. The systems have logged into the IRCTC website to know the number of trains running from X destination to Y destination.
The client system sends the request to the network server. The network server sends the same request to the database and the final result is sent to the client system. This process is conducted when one system sends the request. But in real time, there will be n number of systems and there can be multiple requests that are sent at a time for the same data. The database server will have to process all the requests simultaneously and send back the requested data to the client systems.
Types of Databases
The databases are classified into various databases depending upon the usage requirements.
- Centralized database.
- Distributed database.
- Personal database.
- End-user database.
- Commercial database.
- NoSQL database.
- Operational database.
- Relational database.
- Cloud database.
- Object-oriented database.
- Graph database.
What Is SQL?
Now we are good to go with SQL! As discussed before SQL full form is a structured query language, it helps you to communicate with the database by commands. Here are some of the features of SQL Database:
- It allows users to extract data from relational database.
- It allows to create database and tables.
- It allows updating, inserting, deleting and altering database and tables.
- It provide security and allow to set a permission.
- Allows people to handle data in new ways.
History of SQL
IBM Corporation, Inc. created the language Structured English Query Language (SEQUEL) to implement Codd’s model. Later, SEQUEL was renamed SQL (still pronounced “sequel”). The first commercially available implementation of SQL was released in 1979 by Relational Software, Inc. (now Oracle). SQL is now widely recognised as the standard RDBMS language.
Since SQL can work with any database, it is the most widely used language for database access. The databases in which you interact are programs that allow clients to logically store and manage information. With SQL, we can have the following advantages.
- SQL offers data access to users in relational databases.
- Users may use this feature to define the data.
- Identifying and modifying the data in a database is easy with SQL
- We can create, delete, alter the data in the database anytime.
- It Allows SQL modules, libraries, and pre-compilers to be embedded within other languages
- Database views, stored procedures, and functions can be built with SQL.
When you want to run a SQL command on any DBMS system, you must first decide the best method for carrying out your request, and the SQL engine will determine how to interpret that task.
The following are some important components of the SQL process:
- Query Dispatcher: The dispatcher’s task is to send the query request to either CQE or SQE, depending on the query’s attributes. The dispatcher is in charge of handling all inquiries. It can’t be avoided.
- Optimization Engines: After considering several factors related to the objects referenced and the conditions defined in the query, including the Optimizer Goal, the Query optimizer determines the most efficient way to execute a SQL expression.
- Classic Query Engine: For any fields that are empty, CQE will use default values to map data into the record buffer. For fields that aren’t empty, SQE just maps data to the record buffer.
- SQL Query Engine: To access data in relational structures, a SQL query engine interprets SQL commands and language. Many people use SQL query engines to perform CRUD (create, read, update, and delete) operations and implement data policies that are required by relational data models and database management systems.
Types of SQL Commands
SQL commands are traditionally divided into four categories:
- Data Query Language (DQL Commands in SQL)
- Data Definition Language (DDL Commands in SQL)
- Data Manipulation Language (DML Commands in SQL)
- Data Control Language (DCL Commands in SQL)
Data Query Language (DQL Commands in SQL)
Data Query Language comprises only one command ‘select.’ This command can be accompanied by many other clauses to compose queries.
Data Definition Language (DDL Commands in SQL)
Data Definition Language is power for SQL, which allows a user to create and restructure database objects. The basic DDL commands in SQL are Create Tables, Alter Tables, and Drop Tables.
||It creates a new table
||It deletes the ENTIRE table.
||Modifies the existing table
Data Manipulation Language (DML Commands in SQL)
Data Manipulation Language is used to manipulate data within the tables. The basic DML commands in SQL are Insert, Update and Delete.
||Retrieve information from database
||Add new information to a database
||Modifies the information currently stored in a database
||Delete information from the database
Data Control Access Language (DCL Commands in SQL)
And finally, we have Data Control Access which allows the user to control access to data within the database. These DCA commands are generally used to control the distribution of privileges among users and create objects related to user access. The basic DCL commands in SQL are Grant and Revoke.
This brings us to the end of the Introduction to SQL. Here we have learnt what is SQL, SQL full form, SQL Database, all basic SQL commands and its types – DDL, DCL, DML and DQL with examples.
What is SQL used for?
In the technology world, databases and SQL are used in almost any environment where large volumes of data are involved. The finance industry, music applications, social media platforms are some of the sectors that use SQL the most.
For example, Banking software and payment processors, such as Stripe, store and operate data about financial transactions and users in the finance industry. A complex database is at the heart of these procedures. Furthermore, bank database systems have additional security specifications that necessitate the strictest risk enforcement in the SQL code.
How to Use SQL
With SQL, we can create databases, tables, functions, etc. the following are the SQL commands you need to learn to work in a database.
- CREATE DATABASE – for creating a database
- CREATE TABLE – for creating tables
- SELECT – for finding/extracting some data from a database
- UPDATE – for making adjustments and edit data
- DELETE – for deleting some data
For example, if you want to create a new record in the database.
CREATE DATABASE name_of_a_database;
CREATE TABLE name_of_a_table (
Types of SQL Statements
SQL statements are mainly classified into the following.
- Data Definition Language (DDL) Statements
- Data Manipulation Language (DML) Statements
- Transaction Control Statements
- Session Control Statements
- System Control Statement
- Embedded SQL Statements
SQL is a database management language. It entails database formation, deletion, row retrieval, and modification, among other things. SQL is accepted as the standard language for relational databases by both ANSI and the ISO/IEC. There are many sections of the SQL specifications.
The formal names of this standard are:
ANSI/ISO/IEC 9075:2003, “Database Language SQL”, Parts 1 (“SQL/Framework”), 2 (“SQL/Foundation”), 3 (“SQL/CLI”), 4 (“SQL/Persistent Stored Modules”), 9 (“SQL/Management of External Data”), 10 (“SQL/Object Language Binding”), 11 (“SQL/Schemata”), 13 (“SQL/Java Routines and Types”), 14 (“SQL/XML”) and (“SQL/MDA”)
SQL Language elements
Mostly used SQL language elements are:
Keywords: single or multiple keywords are present in every SQL statement
Expressions: from elements, like constants, SQL operators, Expressions are formed.
Variables: there are many variables like global variables, Sybase IQ supports local variables, and connection-level variables.
Comments: to attach explanatory text to SQL statements or blocks of statements, the comment is used. A comment is not executed in the SQL server.
Strings: Strings may be literal strings or VARCHAR or CHAR data types expressions.
Identifiers: names of objects in the database, like user IDs, tables, and columns can be said as Identifiers.
NULL Value: to specify a value that is unknown, missing, or not applicable, a NULL value is used.
Special values: When creating tables, special values should be used in expressions and as column defaults.
Search conditions: Conditions may be used to pick a subset of a table’s rows or to manipulate statements such as an IF statement to evaluate flow control.
Why does it make sense to learn SQL after NoSQL?
Since NoSQL databases are highly specialized systems with unique use and limitations, we should learn SQL after NoSQL. NoSQL is more suited to those who work with large amounts of data. Relational databases and related technologies are used by the vast majority of people.
Comparing the security and storage support, SQL has more advantages than NoSQL.
SQL Skills in Demand
Most organizations are looking for professionals in SQL skills. Some in-demand SQL skills are:
- Database structures
- Creating a database with SQL
- SQL statements and clauses
- SQL database management
- MySQL and PostgreSQL
- Master PHP
With these in-demand SQL skills you can land in positions as follows:
- Database administrators(DBA)
- Database Migration engineer
- Data scientist
- Big data architect
What’s the Future of SQL Databases?
Now, let’s take a quick ride on what are the SQL Basics we have learned in this blog.
- SQL- SQL is a structured query language
- History of SQL- first implemented in 1979
- Why SQL?- we can create, alter, delete data records in a database anytime
- SQL process- Query dispatcher, optimization engines, classic query engine, the SQL query engine
- Types of SQL commands- DQL, DDL, DML, and DCL.
- SQL language elements- keywords, expressions, variables, comments strings, etc
- SQL skills- database structure, database creation, statements, clauses, MySQL and master PHP, etc