Structured Query Language (SQL)

Structured Query Language

SQL (Structured Query Language) is a database administration language that involves database creation, database deletion, fetching data rows, modifying and deleting data rows, and so on.

SQL stands for Structured Query Language, which is a computer language used to store, manipulate, and retrieve data from a relational database. SQL was created by IBM Computer Scientists in the 1970s and was adopted as an American National Standards Institute (ANSI) and International Organization for Standardization (ISO) standard in 1986 and 1987, respectively.

SQL is the standard language for communicating with relational database systems. All Relational Database Management Systems (RDMS), including MySQL, MS Access, Oracle, Sybase, Informix, Postgres, and SQL Server, employ SQL as their Standard Database Language.

Why is SQL important ?

SQL is an excellent language to learn because it is the principal database language for data processing activities and is utilized in a variety of sectors. 

The following reasons emphasize the need of SQL:

1. Backbone of the data industry 

SQL is regarded as the backbone of the data industry. It is commonly used by data-driven professionals such as data analysts, business analysts, and database developers.

2. In-demand Skill

SQL knowledge is one of the most in-demand data science skills. It appears in a considerable number of data science job listings, indicating that it is a valuable ability for experts in the industry.

3. Data Manipulation 

SQL is ideally suited for data manipulation. It allows users to freely test and change data, making it useful for tasks like filtering, sorting, and aggregating information.

4. Commonality and Compatibility 

SQL is widely used in a variety of IT systems and is interoperable with a number of other languages. Its commonality promotes newcomers to the profession, who are likely to use SQL throughout their careers. It also makes applications easier to use and boosts corporate productivity and efficiency.

What is SQL Command ?

SQL commands are instructions used to interface with databases, allowing communication and executing specified actions and data queries. SQL allows users to perform a wide range of actions, including table creation, data addition to existing tables, table deletion, table structure modification, and user access permissions setting. This language serves as a conduit for users to negotiate the complexity of database management, allowing them to exert precise and efficient control over data structures, content, and security measures.

From table creation to data entry, from querying information to controlling access and security measures, fundamental SQL query commands contain the essence of database management, serving as the driving force behind all database operations. Each SQL command, classified into separate types, plays a specialized role in the complicated dance of data manipulation, ensuring that databases stay organized, efficient, and secure in the hands of skilled SQL practitioners.

Types of  SQL Commands 

1. Data Definition Language (DDL)

DDL (Data Definition Language) refers to acts that affect the structure of tables, such as table creation, deletion, or updates. Essentially, all DDL instructions are auto-committed, which means that any changes performed are stored instantly and permanently in the database.

Here are some commands that come under DDL :

• CREATE

• ALTER

• DROP

• TRUNCATE

2. Data Control Language (DCL)

DCL commands are used to grant and test the authority of any database user.

Here are some commands that come under DCL :

• GRANT

• REVOKE

3. Data Manipulation Language (DML)

DML instructions are used to modify the database, including all forms of changes. 

These commands do not automatically commit changes, suggesting that adjustments cannot be permanently stored in the database. They are susceptible to a rollback.

There are some commands that come under DML :

• INSERT

• UPDATE

• DELETE

4. Transaction Control Language (TCL)

TCL commands can only be used in combination with DML instructions like INSERT, DELETE, and UPDATE. 

These actions are automatically committed to the database, hence they cannot be used during table creation or deletion.

Some example of TCL Commands :

• COMMIT

• ROLLBACK

• SAVEPOINT

5. Data Query Language (DCL)

DQL, or Data Query Language, statements are used to run queries against data stored in schema objects. The basic goal of DQL commands is to retrieve specified schema relations based on the provided query. DQL can be defined as a set of SQL statements used to retrieve data from a database and arrange it in a specific order. This functionality is contained within the SELECT statement.

SELECT extracts data from the database for further actions. When a SELECT statement is executed on one or more tables, the resulting dataset is usually assembled into a temporary table that the application, such as a front-end interface, can subsequently display or access.

Here ,You can check complete article on types of SQL commands: Click Here to Read

History of SQL 

• 1970: E.F. Codd publishes "A Relational Model of Data for Large Shared Data Banks" in Communications of the ACM, establishing the groundwork for RDBM-Ses.

• 1974: IBM researchers publish an essay introducing Structured Query Language, originally known as SEQUEL or Structured English Query Language. The name was altered in order to protect its trademark. 

• 1977: Relational Software Inc., later known as Oracle, begins developing a commercial RDBMS.

• 1979: Oracle ships the first commercially available relational database management system for Digital Equipment Corp.'s minicomputer systems in 1979.

• 1982: IBM introduces the SQL/Data System, a SQL RDBMS for IBM mainframes.

• 1985: IBM releases Database 2, a SQL relational database management solution for the Multiple Virtual Storage mainframe operating system, in 1985.

• 1986: SQL is adopted as a standard in 1986 by an ANSI committee and later ISO.

• 1989: SQL-89, the first revision of the ISO SQL standard, was published in 1989.

• 1992: SQL-92 is the first significant modification of the ISQ SQL standard, published in 1992.

• 1999: ISO/IEC SQL:1999, the first version titled in accordance with ISO naming conventions, introduces programming features and Java support. 

• 2003: ISO/IEC SQL:2003 provides a predefined data type for Extensible Markup Language (XML) objects. 

• 2006: ISO/IEC SQL:2006 improves XML-related capabilities. 

• 2008: ISO/IEC SQL:2008 now supports partitioned JOINs, a mechanism for joining two or more tables that handles them as if they were one table.

• 2011: ISO/IEC SQL:2011 enhances functionality for relational databases with time-related data.

• 2016: ISO/IEC SQL:2016 includes optional new features such as JavaScript Object Notation updates, polymorphic table function support, and row pattern matching.

• 2023: ISO/IEC 9075:2023 is the most recent SQL version, which has been modified in 2023. It is divided into nine segments and is made up of new and updated features that address changing industry needs.

SQL Skills 

SQL skills can be useful in a wide number of fields. Journalists who reported on offshore tax evasion and money laundering in 2013 had to learn SQL to understand the importance of the millions of emails and files that were released.