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The syntax of the SQL programming language is defined and maintained by ISO/IEC SC 32 as part of ISO/IEC 9075. This standard is not freely available. This standard is not freely available. Despite the existence of the standard, SQL code is not completely portable among different database systems without adjustments.
A NOT NULL constraint is functionally equivalent to the following check constraint with an IS NOT NULL predicate: . CHECK (column IS NOT NULL) Some relational database management systems are able to optimize performance when the NOT NULL constraint syntax is used as opposed to the CHECK constraint syntax given above.
A data definition language like SQL presents an interesting case: it can be deemed a domain-specific language because it is specific to a specific domain (in SQL's case, accessing and managing relational databases), and is often called from another application, but SQL has more keywords and functions than many scripting languages, and is often ...
Standard SQL uses a glob-like syntax for simple string matching in its LIKE operator, although the term "glob" is not generally used in the SQL community. The percent sign (%) matches zero or more characters and the underscore (_) matches exactly one.
ISO/IEC 9075 "Information technology - Database languages - SQL" is an international standard for Structured Query Language, and is considered as specifying the minimum for what a database engine should fulfill in terms of SQL syntax, which is called Core SQL. The standard also defines a number of optional features.
SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Edgar F. Codd [12] in the early 1970s. [13] This version, initially called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM's original quasirelational database management system, System R, which a group at IBM San ...
CREATE TABLE employees (id INTEGER PRIMARY KEY, first_name VARCHAR (50) not null, last_name VARCHAR (75) not null, mid_name VARCHAR (50) not null, dateofbirth DATE not null); Some forms of CREATE TABLE DDL may incorporate DML ( data manipulation language )-like constructs, such as the CREATE TABLE AS SELECT (CTaS) syntax of SQL.
The IS NULL and IS NOT NULL predicates (which use a postfix syntax) test whether data is, or is not, Null. [12] The SQL standard contains the optional feature F571 "Truth value tests" that introduces three additional logical unary operators (six in fact, if we count their negation, which is part of their syntax), also using postfix notation.