What is SQL? – SQL in plain language + start guide
Meetings become one of the most valuable assets of organizations and companies. By using data analysis, I can find out the profit and loss of organizations and the information obtained from them can provide useful solutions in order to improve the business. One of the most important and practical tools to process data, manipulate it and provide reports based on data stored in databases, is Structured Query Language.
SQL” (Structured Query Language | SQL)
This article is based on the answer to SQL. In addition to other topics related to the question of who is paid.
In order to answer the question of what QL is, it is necessary to first provide a brief description of the topics related to this similar language, types of databases and “Database Management Systems” (Database Management Systems | DBMS) so that those who are interested in this language. It is better to understand its use. Also, in this article, a brief history of the SQL language, the advantages and disadvantages of this language and the main commands are also mentioned.
What is data and information?
To answer the question of what SQL is, first of all, the concept (data) must be explained because the SQL language is used to access data and change it. Data is raw information that is collected from sources in different formats such as numbers, text, audio and photos. In computer science, data is converted into binary numbers so that they can be processed efficiently. Data in the field of concepts related to the database refers to all the items stored in the form of tables in the database.
For example, a table with the title “Customer” can have a column with the title “Phone Number” that can somehow be received as a text type, and only texts can be stored in this column.
The data is stored in the database in raw form and when a report is prepared from the data or processing is applied to this data, the final result is provided to the user in the form of “information” (information).
For example, a table titled “Bank Account” which contains columns such as “Customer Name”, “Account Type”, “Account Balance”, “Contact Number” and “Address” is given raw products in the form of “Records”. records) or table rows.
When customer accounts are needed, their types are short-term information, thus providing the user with useful information for further review and analysis. In the following, the explanation of the database and how data is stored in it will be discussed.
What is a database?
Before explaining the answer to the question, what is SQL? First, the question of what is a database is addressed, because SQL is used to manage and change database tables.
A collection of raw or structured data stored electronically in a computer system is called a database, database or database.
In other words, I can think of the database as a library where I can store the available books. In this example, the data is library books.
The data is stored in the form of rows and columns and in the form of a table in the database (here, the table means only the tables in the relational database) to enable processing and querying on the data. Using the SQL language, data can be easily accessed, managed, changed, updated, controlled, organized and modified.
In the early 1960s, the first databases were presented, which included two types of “Navigational Database” and “Network Database“.
Trace-based database: Hierarchical databases are a type of trace-based database. The structure of this type of database is in the form of a tree, and records can be found in it by following the references of the records. In this type of database, only one-to-many relationships are used to create relationships between tables.
Network database: In this type of database, the modeling of “Entity” is such that each “Child Entity” can have more than one “Parent Entity”.
It was easy to work with these two types of databases, but they did not have high flexibility. For this reason, in the 1980s, “Relational Database” (Relational Database) was proposed, which will be explained below.
What is a relational database?
Answering the question “What is SQL” also requires an understanding of the relational database concept. A relational database is a type of database that can be used to store data in multiple related tables. The relational database structure is similar to Excel spreadsheets.
Database tables can be considered the same as “extended layers” (Sheets) of the Excel program. Each table in the database contains rows and columns where the rows represent data values and the columns represent “attributes”.
In order to access the database and use the SQL language to process the data, a “Database Management System” (DBMS) is used.
What is a database management system?
To get the answer to the question “What is the SQL language and what is its application”, one should also understand the concept of database management system and its relationship with the SQL language. A database management system is software that can be installed on a personal computer or server and used to manage databases.
One of the types of database management systems is called “Relational Database Management System” (RDBMS), which is used to create, update, manage and perform various processes on the database. With RDBMS, data can be stored in the form of a table and querying can be done using the SQL language.
The most common relational database management systems that use SQL are listed below:
- Sybase
- Microsoft SQL Server
- Oracle
- Ingres
- Access
After explaining the necessary concepts related to the SQL language, in the next section, the question of what is the SQL language and what are its uses will be answered?
What is SQL?
“Structured query language”. SQL (Structured Query Language | SQL) is a language used to manage and communicate with the database. In other words, this language can be used to create a database, delete and update information, and extract data from a relational database. This language is one of the American National Standard Institute (ANSI) languages, which was presented by IBM researchers in 1970.
Other versions of this language such as T-SQL and PSQL have also been developed by other companies such as Microsoft and Interbase/Firebird. Although there was an effort to standardize the use of this language, some commands of this language are different in different relational databases.
The capabilities that the SQL language provides to its users are as follows:
The SQL language allows users to access data in an RDBMS.
With the SQL language, the data in the relational database can be described.
The SQL language allows users to store data and manipulate it.
You can access the data in the database with SQL libraries in other programming languages and using SQL commands.
With the SQL language, you can create and delete the database and all the objects in it, such as tables, routines, views, and other items.
Using the SQL language, different users can be given different access levels and manage how to access the data stored in the database.
What is the history of SQL language?
Now that the question “What is SQL language” has been answered, in this section, the history of this language and its evolution will be discussed.
The first computerized databases were introduced in the late 1960s. In this decade, many computer science researchers focused on improving working with databases. One of these researchers was Edgar Frank Ted Codd, who worked as a computer engineer at IBM.
In 1970, Codd introduced relational databases in computer science by presenting an article entitled (A Rational Model of Data for Large Shared Data Banks). Thus, most of the time, this person is mentioned as the person who presented the SQL language for the first time.
When Codd published his paper, people were using Network Databases and Hierarchical Databases. These databases did not have flexibility. In other words, in order to extract data from these databases, programming had to be used and non-programmers could not access the data.
History of the SQL language
In his article, Codd proposed a new idea using the mathematical concept of relationships based on data modeling, which today are called tables. This type of database was more flexible compared to network and hierarchical databases, and it was possible to add new relationships to previous relationships without the need to change the existing relationships, and thus, it became easier to work with the database.
System R project
When the Codd model was proposed in 1970, it was not well received and IBM abandoned the implementation of Codd’s proposal and idea. At the time, IBM researchers were working with a hierarchical database called IMS. Three years later, in 1973, IBM started a project called System R to explore Codd’s ideas about the relational data model. At that time, Codd did not work closely with the System R project development team, and two other researchers, Don Chamberlin and Ray Boyce, were responsible for implementing the query language.
