What Does Structured Query Language [SQL] Mean?
Structured Query Language [SQL] is a programming language that is typically used in relational database or data stream management systems.
It was developed by IBM in the early 1970s and is now an official standard recognized by the American National Standards Institute [ANSI] and the International Organization for Standardization [ISO].
Techopedia Explains Structured Query Language [SQL]
SQL has remained a consistently popular choice for database users over the years primarily due to its ease of use and the highly effective manner in which it queries, manipulates, aggregates data and performs a wide range of other functions to turn massive collections of structured data into usable information.
For this reason, it has been incorporated into numerous commercial database products, such as MySQL, Oracle, Sybase, SQL Server, Postgres and others. In fact, many non-relational databases like MongoDB and DynamoBD are called NoSQL products due to their lack of SQL programming.
While different iterations of SQL may utilize different syntax for key operations, in general, basic commands like select, insert, update and create are common to all SQL releases. This makes it very easy for someone with a basic knowledge of SQL to work in many different environments and perform a wide variety of tasks.
Four Categories of SQL Commands
Data Definition Language [DDL]
This includes CREATE [tables, views, objects, etc.], ALTER and DROP [delete].
Data Manipulation Language [DML]
SELECT, INSERT, UPDATE, DELETE of records within tables.
Data Control Language [DCL]
GRANT and/or REVOKE user privileges, etc.
Database Indexing
CREATE INDEX and DROP INDEX statements are used to create and delete indexes in tables.
Streamlining Search and Other Functions
SQL also allows users to build constraints onto tables or columns to restrict the type of data they contain. This helps ensure data accuracy and relevancy, and simplifies overall database management by streamlining search and other functions.
Some examples of SQL constraints include:
NOT NULL
Which prevents columns from having a null value.
UNIQUE
To ensure all values are different.
In addition, DBAs can use SQL to build integrity into the database by preventing the creation of duplicate rows, allowing only the entry of valid data, forbidding deletion of data tied to multiple records, and other functions.
At the same time, however, SQL provides a number of normalization tools designed to streamline data dependencies and in general reduce the size and scope of the database to make it operationally effective and resource efficient.
Obviously, SQL is not the best choice for all database applications, otherwise there would be no alternatives. For one thing, while SQL had been effective at data scales up through the 1990s and beyond, the implementation and relational database management systems [rather than the language itself] started to falter at the hyperscale levels at the turn of the century.
Some users also complain of its sharding limitations, which hamper the ability to break large databases into smaller, more manageable ones.
These drawbacks, in fact, are what led to the creation of NoSQL and the more recent NewSQL, which attempts to enhance traditional SQL’s scalability without sacrificing its inherent atomicity, consistency, isolation and durability [ACID].
SQL is a language to operate databases; it includes database creation, deletion, fetching rows, modifying rows, etc. SQL is an ANSI [American National Standards Institute] standard language, but there are many different versions of the SQL language.
What is SQL?
SQL is Structured Query Language, which is a computer language for storing, manipulating and retrieving data stored in a relational database.
SQL is the standard language for Relational Database System. All the Relational Database Management Systems [RDMS] like MySQL, MS Access, Oracle, Sybase, Informix, Postgres and SQL Server use SQL as their standard database language.
Also, they are using different dialects, such as −
- MS SQL Server using T-SQL,
- Oracle using PL/SQL,
- MS Access version of SQL is called JET SQL [native format] etc.
Why SQL?
SQL is widely popular because it offers the following advantages −
Allows users to access data in the relational database management systems.
Allows users to describe the data.
Allows users to define the data in a database and manipulate that data.
Allows to embed within other languages using SQL modules, libraries & pre-compilers.
Allows users to create and drop databases and tables.
Allows users to create view, stored procedure, functions in a database.
Allows users to set permissions on tables, procedures and views.
A Brief History of SQL
1970 − Dr. Edgar F. "Ted" Codd of IBM is known as the father of relational databases. He described a relational model for databases.
1974 − Structured Query Language appeared.
1978 − IBM worked to develop Codd's ideas and released a product named System/R.
1986 − IBM developed the first prototype of relational database and standardized by ANSI. The first relational database was released by Relational Software which later came to be known as Oracle.
SQL Process
When you are executing an SQL command for any RDBMS, the system determines the best way to carry out your request and SQL engine figures out how to interpret the task.
There are various components included in this process.
These components are −
- Query Dispatcher
- Optimization Engines
- Classic Query Engine
- SQL Query Engine, etc.
A classic query engine handles all the non-SQL queries, but a SQL query engine won't handle logical files.
Following is a simple diagram showing the SQL Architecture −
SQL Commands
The standard SQL commands to interact with relational databases are CREATE, SELECT, INSERT, UPDATE, DELETE and DROP. These commands can be classified into the following groups based on their nature −
DDL - Data Definition Language
| 1 | CREATE Creates a new table, a view of a table, or other object in the database. |
| 2 | ALTER Modifies an existing database object, such as a table. |
| 3 | DROP Deletes an entire table, a view of a table or other objects in the database. |
DML - Data Manipulation Language
| 1 | SELECT Retrieves certain records from one or more tables. |
| 2 | INSERT Creates a record. |
| 3 | UPDATE Modifies records. |
| 4 | DELETE Deletes records. |
DCL - Data Control Language
| 1 | GRANT Gives a privilege to user. |
| 2 | REVOKE Takes back privileges granted from user. |