Free Online SQL Escape

SQL is a domain-specific language used in programming and designed for managing data held in a relational database management system (RDBMS), or for stream processing in a relational data stream management system (RDSMS). It is particularly useful in handling structured data, i.e. data incorporating relations among entities and variables.

SQL offers two main advantages over older read–write APIs such as ISAM or VSAM. Firstly, it introduced the concept of accessing many records with one single command. Secondly, it eliminates the need to specify how to reach a record, e.g. with or without an index.

Originally based upon relational algebra and tuple relational calculus, SQL consists of many types of statements, which may be informally classed as sublanguages, commonly: a data query language (DQL),[a] a data definition language (DDL),[b] a data control language (DCL), and a data manipulation language (DML).[c] The scope of SQL includes data query, data manipulation (insert, update and delete), data definition (schema creation and modification), and data access control. Although SQL is essentially a declarative language (4GL), it includes also procedural elements.

SQL was one of the first commercial languages to utilize Edgar F. Codd’s relational model. The model was described in his influential 1970 paper, "A Relational Model of Data for Large Shared Data Banks". Despite not entirely adhering to the relational model as described by Codd, it became the most widely used database language.

SQL became a standard of the American National Standards Institute (ANSI) in 1986, and of the International Organization for Standardization (ISO) in 1987. Since then, the standard has been revised to include a larger set of features. Despite the existence of such standards, most SQL code is not completely portable among different database systems without adjustments.

In computing and telecommunication, an escape character is a character which invokes an alternative interpretation on subsequent characters in a character sequence. An escape character is a particular case of metacharacters. Generally, the judgment of whether something is an escape character or not depends on context.

An escape character may not have its own meaning, so all escape sequences are of two or more characters.

Escape characters are part of the syntax for many programming languages, data formats, and communication protocols. For a given alphabet an escape character's purpose is to start character sequences (so named escape sequences), which have to be interpreted differently from the same characters occurring without the prefixed escape character.

There are usually two functions of escape sequences. The first is to encode a syntactic entity, such as device commands or special data, which cannot be directly represented by the alphabet. The second use, referred to as character quoting, is to represent characters, which cannot be typed in current context, or would have an undesired interpretation. In the latter case an escape sequence is a digraph consisting of an escape character itself and a "quoted" character.

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