What is SQL – Must-Know SQL Commands with Example
It is the RDBMS’s Structured Query Language. Learn the kinds of all fundamental SQL commands, including DDL, DCL, DML, and DQL, with examples. You will learn everything you need to know about SQL in our SQL Training Institute in Chennai with IBM Certification in Softlogic Systems.
What is SQL?
SQL is a domain-specific language. It is employed in programming languages for applications to allow programmers to interact with the data. A relational database is used to store the data. We have relational database management systems, which employ SQL as a standard database language, to manage this data. Examples include SQL Server, MySQL, MS Access, and others.
What exactly does SQL mean?
“What is the entire form of SQL?” is a frequently asked question. Structured Query Language is known as SQL. The language was originally known as SEQUEL and was developed in 1970 for the IBM System R research database. However, the name was changed to SQL due to copyright concerns.
What is Data?
Data are discrete pieces of information that are kept in or used by a computer. These pieces of information can be facts, numbers, or specifics. Learning what SQL is and how it functions may take a while in this digital age where data drives all we do.
What is Database?
A well-organized group of data that is kept in an electronic format is called a database. An electronic system that makes it simple for users to access, modify, and update data is known as a SQL database.
What Is a Database Management System?
Consider a school SQL database that contains information about current students as well as students who have previously studied in the Student Details table. Similar information may be found there regarding the faculty, management, staff, and many more groups, depending on the needs of the school. We need a database management system to manage vast volumes of data.
Nowadays, a database management system is used to handle almost all databases (DBMS). In general, it is system software used to manage databases and create data in a methodical manner.
How does SQL Database Works?
DBMS offers a fundamental method for creating, retrieving, updating, and managing data for both users and programmers. Take the case of a student XYZ who wants to alter his address. The user edits the information after the DBMS searches for it in the table “Student Details” of the database “School Database” and displays it to them.
Types of Database Architecture?
There are two types of database architecture as follows
- File Server
File Server Architecture
The local system is where files are located in the file server architecture. It is helpful for network-wide information sharing. Over the network, the client requests a file, which the file server then transmits to the client. This is thought to be the most basic data service available for information exchange over a network. Remote server processors can also access the file server.
Here is an illustration to help you comprehend how the file server is implemented.
Consider that one of your pals asks you to send them an Excel file so they may get some information. You then send your friend a copy. Now, any modifications you make to your original Excel file won’t be reflected in the one that your friend has access to.
In this illustration, your friend’s gadget is the one seeking the information, and you are the file server. By stating that the server serves as a sorting device and that only one person at a time can access it, we can draw a conclusion about the file server architecture.
Any application that consumes the data is a client in a client-server architecture, while the database serves as the server.
Here is an illustration that shows how this server functions. Think about three client systems or OLE DB components that are simultaneously accessing the database. The systems have accessed the IRCTC website to learn how many trains are traveling from X to Y destinations.
The network server receives the request from the client system. The same request is sent by the network server to the database, and the response is then provided to the client system. When one system sends the request, this procedure starts. However, in real-time, there will be n systems and n simultaneous requests for the same data may be made. All queries must be handled concurrently by the database server, which must then return the requested data to the client systems.
Types of Databases
Depending on the usage needs, the databases are divided into different categories as follows
- Centralized database.
- Distributed database.
- Personal database.
- End-user database.
- Commercial database.
- NoSQL database.
- Operational database.
- Relational database.
- Cloud database.
- Object-oriented database.
- Graph database.
Features of SQL
Now that SQL is ready, we can use it! As was previously mentioned, SQL is a structured query language that enables command-based communication with databases. Here are a few characteristics of the SQL Database:
- Users can extract data from the relational database using this.
- Users can make databases and tables using it.
- It permits changing databases and tables by inserting, removing, and moving them around.
- Security is offered, and permissions can be configured.
- Enables new data handling techniques.
History of SQL
IBM Corporation, Inc. created the language Structured English Query Language to implement Codd’s model (SEQUEL). Later, SQL replaced SEQUEL and is still called “sequel.” The first commercial SQL implementation was released by Relational Software, Inc. in 1979. (now Oracle). Today, SQL is largely accepted as the mandated RDBMS language.
SQL is the most used language for database access because it can be used with any database. The databases with which you work are applications that let users logically store and manage data. We can benefit from the following things from SQL.
- Users of relational databases can access data using SQL.
- This feature can be used by users to define the data.
- SQL makes it simple to locate and change the data in a database.
- Data in the database can be added, removed, or changed at any moment.
- It enables the embedding of SQL modules, libraries, and pre-compilers into other languages.
- SQL can be used to create database views, stored procedures, and functions.
Any DBMS system that supports SQL queries requires you to first choose the best way to execute your request; the SQL engine will then choose how to interpret it.
Some significant elements of the SQL procedure include the following:
Query Dispatcher: Depending on the properties of the query, the dispatcher must transmit the query request to either CQE or SQE. All inquiries must be handled by the dispatcher. It is unavoidable.
Optimization Engines: The query optimizer chooses the most effective way to execute a SQL expression after taking into account a number of elements relating to the objects referenced and the conditions specified in the query, such as the optimizer goal.
Classic Query Engine: CQE will utilize default values to map data into the record buffer for any fields that are empty. SQE simply maps data to the record buffer for fields that don’t have any empty values.
SQL Query Engine: It decodes SQL commands and language to access data in relational structures. The CRUD (create, read, update, and delete) activities and data policies mandated by relational data models and database management systems are frequently carried out using SQL query engines.
Types of SQL Commands
Generally, there are four sorts of SQL commands:
- Data Query Language (SQL DQL Commands)
- Data Definition Language (SQL DDL Commands)
- Data Manipulation Language (SQL DML Commands)
- Data Control Language (SQL DCL Commands)
Data Query Language (SQL DQL Commands)
The command “select” is the only one in Data Query Language. To create queries, this command can be used with a variety of additional clauses.
Data Definition Language (SQL DDL Commands)
The power of SQL is the ability to build and rearrange database objects using the Data Definition Language. Create Tables, Alter Tables, and Drop Tables are the three fundamental DDL commands in SQL.
CREATE TABLE – It is for creating a new table
DROP TABLE – It is used to delete the entire table
ALTER TABLE – It is used to update the existing table
Data Manipulation Language (SQLDML Commands)
The tables’ data can be changed using data manipulation language. Insert, Update, and Delete are the three fundamental DML commands in SQL.
SELECT – It is used to retrieve information from the database
INSERT – It is used to add new information to the database
UPDATE – It is used to update the information stored in a database
DELETE – It is used to delete the information from the database
Data Control Access Language (SQL DCL Commands)
Finally, data control access lets the user manage who has access to what data is in the database. Typically, these DCA commands are used to establish objects related to user access and manage how privileges are distributed among users. The fundamental DCL SQL commands are Grant and Revoke.
Why should use SQL?
In the realm of technology, SQL and databases are employed in practically every setting where there are substantial amounts of data present. Some of the industries that use SQL the most are the financial sector, music applications, and social media platforms.
For instance, data on financial transactions and users in the finance business is stored and managed by banking software and payment processors like Stripe. These processes are based on a sophisticated database. Additionally, bank database systems require the strongest risk enforcement in the SQL code due to additional security requirements.
How to use SQL?
We can create databases, tables, functions, and other things with SQL. You must master the following SQL commands in order to interact with databases.
CREATE DATABASE is used to create databases.
For constructing tables, use CREATE TABLE.
SELECT is used to locate or extract data from databases.
UPDATE: used to modify and change data.
DELETE is used to delete data.
For Example, if we have to add a new record to the database
CREATE DATABASE name_of_a_database;
CREATE TABLE name_of_a_table (
Types of SQL Commands
These categories best describe how SQL statements are categorized.
- Data Definition Language (DDL) Statements
- Data Manipulation Language (DML) Statements
- Transaction Control Statements
- Session Control Statements
- System Control Statement
- Embedded SQL Statements
A database management language is SQL. It includes, among other things, database creation, deletion, row retrieval, and change. Both ANSI and the ISO/IEC recognize SQL as the de facto language for relational databases. The SQL requirements are divided into numerous sections.
These are the official titles of this standard:
ANSI/ISO/IEC 9075:2003, “Database Language SQL”,
4 (“SQL/Persistent Stored Modules”),
9 (“SQL/Management of External Data”),
10 (“SQL/Object Language Binding”),
13 (“SQL/Java Routines and Types”),
14 (“SQL/XML”) and (“SQL/MDA”)
SQL Language Elements
The most common SQL language components are:
Keywords: Each SQL statement contains one or more keywords.
Expressions: They are created from constituent parts such as constants and SQL operators.
Variables: Sybase IQ supports local variables, connection-level variables, global variables, and many others.
Comments: They are used to provide explanatory text to individual SQL statements or groups of statements. The SQL server does not actually execute a comment.
Strings: Strings can be literal strings or expressions of the VARCHAR/CHAR data types.
Identifiers: Identifiers are the names of database objects, such as user IDs, tables, and columns.
NULL value: It is used to express a value that is unknowable, absent, or not applicable.
Special values: When making tables, special values ought to be utilized as column defaults and in expressions.
Search conditions: Conditions can be used to edit statements like an IF statement to assess flow control or to choose a subset of a table’s rows.
Why is learning SQL after NoSQL a good idea?
We should study SQL after NoSQL since NoSQL databases are extremely specialized systems with distinct uses and limits. People that work with plenty of data are better suited for NoSQL. A majority of individuals use relational databases and related technologies.
When comparing security and storage support, SQL outperforms NoSQL.
SQL Skills in Demand
The majority of employers seek professionals with SQL expertise. Several SQL abilities in demand are:
- Database structures
- Creating a database with SQL
- SQL statements and clauses
- SQL database management
- MySQL and PostgreSQL
- Master PHP
You could land a job in the following fields with these in-demand SQL skills:
What is the Future of SQL Databases?
Let’s quickly review the SQL Fundamentals that we taught in this blog post about what SQL is.
A structured query language is SQL.
SQL’s earliest implementation dates back to 1979.
- At any time, we can add, edit, or remove data records from a database.
- The SQL query engine, the traditional query engine, and query dispatchers are all components of the SQL process.
- SQL DQL, DDL, DML, and DCL command types
- Elements of the SQL language, such as keywords, expressions, variables, and comment strings
- SQL Skills include database design, database development, statements, clauses, MySQL, and PHP proficiency, among others.