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Overview of SQL

Structured Query Language (SQL) is a specialized programming language. Like other popular relational databases, SQL is used by all programs and users to access data in seekdb. Even though some platforms and tools allow users to access databases through interfaces or GUIs, they still use SQL at the underlying level.

History of SQL​

In June 1970, Dr. E. F. Codd from the San Jose, California laboratory of IBM published a paper titled "A Relational Model of Data for Large Shared Data Banks" in the Association for Computing Machinery (ACM) journal and introduced the concept of the relational model.

In 1974, D. D. Chamberlin and R. F. Boyce from the same laboratory developed a standardized language called SEQUEL (Structured English QUEry Language) for the relational database system SystemR developed by IBM. In November 1976, they published the new version of SQL (called SEQUEL/2) in the IBM Journal of R&D. In 1980, SEQUEL/2 was renamed SQL.

In 1979, Oracle introduced the first commercial SQL implementation, and IBM also implemented SQL in its DB2 and SQL/DS database systems.

Today, SQL has become the standard language for relational database management systems (RDBMS).

SQL standards​

In October 1986, the American National Standards Institute (ANSI) adopted SQL as the standard language for RDBMS and named it ANSI X3.135-1986. Later, the International Organization for Standardization (ISO) also adopted SQL as an international standard.

In 1989, ANSI adopted and used the SQL standard language defined in the ANSI X3.135-1989 report and called it ANSI SQL 89. This standard replaced the previous ANSI X3.135-1986 version.

The following is a brief history of SQL development:

  • 1986: ANSI X3.135-1986, ISO/IEC 9075:1986, SQL-86.

  • 1989: ANSI X3.135-1989, ISO/IEC 9075:1989, SQL-89.

  • 1992: ANSI X3.135-1992, ISO/IEC 9075:1992, SQL-92 (SQL2).

  • 1999: ISO/IEC 9075:1999, SQL:1999 (SQL3).

  • 2003: ISO/IEC 9075:2003, SQL:2003.

  • 2008: ISO/IEC 9075:2008, SQL:2008.

  • 2011: ISO/IEC 9075:2011, SQL:2011.

Currently, most of the content covered in the mentioned SQL standards is the most fundamental and core part of SQL 92. seekdb also follows the SQL 92 standard and supports some important features from later SQL standards.

How SQL works​

SQL is the interface used to access relational databases such as seekdb, Oracle, and MySQL. All SQL statements are commands for operating on databases.

Typically, SQL can be divided into the following five parts:

  • Data Query Language (DQL): Also known as a data retrieval language, it is used to retrieve data from tables and describe how to return the data to programs for output. DQL does not modify the data stored in the database.

  • Data Manipulation Language (DML): It is used to modify the data stored in the database, including adding, modifying, and deleting data.

  • Transaction Control Language (TCL): It ensures the integrity and consistency of the database. All DML statements within the same transaction either succeed or fail together.

  • Data Control Language (DCL): It consists of commands for controlling data access permissions. These commands can control the access permissions of specific accounts to specific database resources.

  • Data Definition Language (DDL): It is used to define, modify, and delete resources in the database, such as creating and dropping tables.

Portability of SQL​

SQL is the standard language for accessing databases. All major relational databases support SQL, so programs written in SQL are portable. Typically, only minor modifications are needed to port a program from one relational database to another.

Conventions​

  • Bold indicates graphical user interface (GUI) elements associated with operations or terms defined in the text or glossary.

  • The case of reserved words, keywords, identifiers, and parameters is not case-sensitive. For readability and identification, these words are written in uppercase.

  • SQL statements terminate differently in various programming environments. In this document, a semicolon (;) is used to indicate the end of an SQL statement.

  • Inline code indicates code referenced in the document.

  • To highlight important information, the document will use bold text for terms like "Note", "Important", and "Caution".

  • Optional parameters in the document are enclosed in square brackets, for example, [-n, -quiet].

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