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36-459: QUEL statements are always defined by tuple variables , which can be used to limit queries or return result sets. Consider this example, taken from one of the first original Ingres papers: Here E is a tuple variable that ranges over the EMPLOYEE relation, and all tuples in that relation are found which satisfy the qualification `E.Name = "Jones"`. The result of the query is a new relation W, which has

72-631: 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 multiple times to include a larger set of features and incorporate common extensions. Despite the existence of standards, virtually no implementations in existence adhere to it fully, and most SQL code requires at least some changes before being ported to different database systems. SQL

108-543: A delimiter, as opposed to a data type. Changing the into to a from reverses the process. Similar commands are available in many SQL systems, but usually as external tools, as opposed to being internal to the SQL language. This makes them unavailable to stored procedures . QUEL has an extremely powerful aggregation capability. Aggregates can be nested, and different aggregates can have independent by-lists and/or restriction clauses. For example: This example illustrates one of

144-474: A local RDB and receive tables of data and status indicators in reply from remote RDBs. SQL statements can also be compiled and stored in remote RDBs as packages and then invoked by package name. This is important for the efficient operation of application programs that issue complex, high-frequency queries. It is especially important when the tables to be accessed are located in remote systems. The messages, protocols, and structural components of DRDA are defined by

180-424: A roadblock to full use of SQL's user-defined types. JSON support, for example, needed to be added by a new standard in 2016. The concept of Null is the subject of some debate . The Null marker indicates the absence of a value, and is distinct from a value of 0 for an integer column or an empty string for a text column. The concept of Nulls enforces the 3-valued-logic in SQL , which is a concrete implementation of

216-419: A simple session that creates a table, inserts a row into it, and then retrieves and modifies the data inside it and finally deletes the row that was added (assuming that name is a unique field). Another feature of QUEL was a built-in system for moving records en-masse into and out of the system. Consider this command: which creates a comma-delimited file of all the records in the student table. The d1 indicates

252-493: A single domain COMP that has been calculated for each qualifying tuple. Additional queries can then be made against the relation W. An equivalent SQL statement is: In this example, the relation is being stored in a new table W. This is not a direct analog of the QUEL version; relations in QUEL are more similar to temporary tables seen in most modern SQL implementations. Here is a sample of

288-500: A table. Stored-procedure flow-control statements typically include IF , WHILE , LOOP , REPEAT , and CASE statements, and more. Stored procedures can receive variables, return results or modify variables and return them, depending on how and where the variable is declared. Stored procedures are similar to user-defined functions (UDFs). The major difference is that UDFs can be used like any other expression within SQL statements, whereas stored procedures must be invoked using

324-449: A transaction such that transactions are effectively transparent to them. Stored procedures can also be invoked from a database trigger or a condition handler. For example, a stored procedure may be triggered by an insert on a specific table, or update of a specific field in a table, and the code inside the stored procedure would be executed. Writing stored procedures as condition handlers also allows database administrators to track errors in

360-473: Is a domain-specific language used to manage data, especially in a relational database management system (RDBMS). It is particularly useful in handling structured data , i.e., data incorporating relations among entities and variables. Introduced in the 1970s, SQL offered 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

396-576: Is a subroutine available to applications that access a relational database management system (RDBMS). Such procedures are stored in the database data dictionary . Uses for stored procedures include data-validation (integrated into the database) or access-control mechanisms. Furthermore, stored procedures can consolidate and centralize logic that was originally implemented in applications. To save time and memory, extensive or complex processing that requires execution of several SQL statements can be saved into stored procedures, and all applications call

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432-461: Is a term applied to executable code stored on a blockchain as opposed to an RDBMS. Despite the execution result consensus mechanisms of public blockchain networks differing in principle from traditional private or federated databases, they perform ostensibly the same function as stored procedures, albeit usually with a sense of value transaction. SQL Structured Query Language ( SQL ) ( pronounced S-Q-L ; or alternatively as "sequel")

468-440: Is essentially a declarative language ( 4GL ), it also includes procedural elements. SQL was one of the first commercial languages to use 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 , SQL became the most widely used database language. SQL became

504-540: The CALL statement. or The exact and correct implementation of stored procedures varies from one database system to the other. Most major database vendors support them in some form. Depending on the database system, stored procedures can be implemented in a variety of programming languages , for example SQL , Java , C , or C++ . Stored procedures written in non-SQL languages may or may not execute SQL statements themselves. The increasing adoption of stored procedures led to

540-485: The Distributed Data Management Architecture . Distributed SQL processing ala DRDA is distinctive from contemporary distributed SQL databases. SQL deviates in several ways from its theoretical foundation, the relational model and its tuple calculus. In that model, a table is a set of tuples, while in SQL, tables and query results are lists of rows; the same row may occur multiple times, and

576-605: The database , while prior versions of SQL Server were restricted to unmanaged extended stored procedures primarily written in C. PostgreSQL lets users write functions in a wide variety of languages—including Perl , Python , Tcl , JavaScript (PL/V8) and C. SQL implementations are incompatible between vendors and do not necessarily completely follow standards. In particular, date and time syntax, string concatenation, NULL s, and comparison case sensitivity vary from vendor to vendor. PostgreSQL and Mimer SQL strive for standards compliance, though PostgreSQL does not adhere to

612-485: The 1970s. Chamberlin and Boyce's first attempt at a relational database language was SQUARE (Specifying Queries in A Relational Environment), but it was difficult to use due to subscript/superscript notation. After moving to the San Jose Research Laboratory in 1973, they began work on a sequel to SQUARE. The original name SEQUEL, which is widely regarded as a pun on QUEL , the query language of Ingres ,

648-535: The ISO in 1987. It is maintained by ISO/IEC JTC 1, Information technology, Subcommittee SC 32, Data management and interchange . Until 1996, the National Institute of Standards and Technology (NIST) data-management standards program certified SQL DBMS compliance with the SQL standard. Vendors now self-certify the compliance of their products. The original standard declared that the official pronunciation for "SQL"

684-449: The arguably less desirable quirks of QUEL, namely that all string comparisons are potentially pattern matches. y.str = "ii*" matches all y.str values starting with ii . In contrast, SQL uses = only for exact matches, while like is used when pattern matching is required. Stored procedure A stored procedure (also termed prc , proc , storp , sproc , StoPro , StoredProc , StoreProc , sp , or SP )

720-404: The general 3-valued logic . Another popular criticism is that it allows duplicate rows, making integration with languages such as Python , whose data types might make accurately representing the data difficult, in terms of parsing and by the absence of modularity. This is usually avoided by declaring a primary key, or a unique constraint, with one or more columns that uniquely identify a row in

756-525: The introduction of procedural elements to the SQL language in the SQL:1999 and SQL:2003 standards in the part SQL/PSM . That made SQL an imperative programming language . Most database systems offer proprietary and vendor-specific extensions, exceeding SQL/PSM. A standard specification for Java stored procedures exists as well as SQL/JRT . In some systems, stored procedures can be used to control transaction management; in others, stored procedures run inside

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792-522: The late 1970s, Relational Software, Inc. (now Oracle Corporation ) saw the potential of the concepts described by Codd, Chamberlin, and Boyce, and developed their own SQL-based RDBMS with aspirations of selling it to the U.S. Navy , Central Intelligence Agency , and other U.S. government agencies. In June 1979, Relational Software introduced one of the first commercially available implementations of SQL, Oracle V2 (Version2) for VAX computers. By 1986, ANSI and ISO standard groups officially adopted

828-466: The most popular commercial and proprietary SQL DBMSs, are Oracle (whose DATE behaves as DATETIME , and lacks a TIME type) and MS SQL Server (before the 2008 version). As a result, SQL code can rarely be ported between database systems without modifications. Several reasons for the lack of portability between database systems include: SQL was adopted as a standard by the ANSI in 1986 as SQL-86 and

864-575: The need to specify how to reach a record, i.e., 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: Data query Language (DQL), Data Definition Language (DDL), Data Control Language (DCL), and Data Manipulation Language (DML). 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

900-556: The order of rows can be employed in queries (e.g., in the LIMIT clause). Critics argue that SQL should be replaced with a language that returns strictly to the original foundation: for example, see The Third Manifesto by Hugh Darwen and C.J. Date (2006, ISBN   0-321-39942-0 ). Early specifications did not support major features, such as primary keys. Result sets could not be named, and subqueries had not been defined. These were added in 1992. The lack of sum types has been described as

936-427: The pattern: ISO/IEC 9075-n:yyyy Part n: title , or, as a shortcut, ISO/IEC 9075 . Interested parties may purchase the standards documents from ISO, IEC, or ANSI. Some old drafts are freely available. ISO/IEC 9075 is complemented by ISO/IEC 13249: SQL Multimedia and Application Packages and some Technical reports . A distinction should be made between alternatives to SQL as a language, and alternatives to

972-468: The procedures. One can use nested stored procedures by executing one stored procedure from within another. Stored procedures may return result sets , i.e., the results of a SELECT statement. Such result sets can be processed using cursors , by other stored procedures, by associating a result-set locator, or by applications. Stored procedures may also contain declared variables for processing data and cursors that allow it to loop through multiple rows in

1008-489: The relational model itself. Below are proposed relational alternatives to the SQL language. See navigational database and NoSQL for alternatives to the relational model. Distributed Relational Database Architecture (DRDA) was designed by a workgroup within IBM from 1988 to 1994. DRDA enables network-connected relational databases to cooperate to fulfill SQL requests. An interactive user or program can issue SQL statements to

1044-618: The standard "Database Language SQL" language definition. New versions of the standard were published in 1989, 1992, 1996, 1999, 2003, 2006, 2008, 2011, 2016 and most recently, 2023. The SQL language is subdivided into several language elements, including: SQL is designed for a specific purpose: to query data contained in a relational database . SQL is a set -based, declarative programming language , not an imperative programming language like C or BASIC . However, extensions to Standard SQL add procedural programming language functionality, such as control-of-flow constructs. In addition to

1080-572: The standard SQL/PSM extensions and proprietary SQL extensions, procedural and object-oriented programmability is available on many SQL platforms via DBMS integration with other languages. The SQL standard defines SQL/JRT extensions (SQL Routines and Types for the Java Programming Language) to support Java code in SQL databases. Microsoft SQL Server 2005 uses the SQLCLR (SQL Server Common Language Runtime) to host managed .NET assemblies in

1116-571: The standard in all cases. For example, the folding of unquoted names to lower case in PostgreSQL is incompatible with the SQL standard, which says that unquoted names should be folded to upper case. Thus, according to the standard, Foo should be equivalent to FOO , not foo . Popular implementations of SQL commonly omit support for basic features of Standard SQL, such as the DATE or TIME data types. The most obvious such examples, and incidentally

QUEL query languages - Misplaced Pages Continue

1152-718: The system with greater detail by using stored procedures to catch the errors and record some audit information in the database or an external resource like a file. Prepared statements take an ordinary statement or query and parameterize it so that different literal values can be used at a later time. Like stored procedures, they are stored on the server for efficiency and provide some protection from SQL injection attacks. Although simpler and more declarative, prepared statements are not ordinarily written to use procedural logic and cannot operate on variables. Because of their simple interface and client-side implementations, prepared statements are more widely reusable between DBMS. Smart contract

1188-607: The table. In a sense similar to object–relational impedance mismatch , a mismatch occurs between the declarative SQL language and the procedural languages in which SQL is typically embedded. The SQL standard defines three kinds of data types (chapter 4.1.1 of SQL/Foundation): Constructed types are one of ARRAY, MULTISET, REF(erence), or ROW. User-defined types are comparable to classes in object-oriented language with their own constructors, observers, mutators, methods, inheritance, overloading, overwriting, interfaces, and so on. Predefined data types are intrinsically supported by

1224-417: Was an initialism : / ˌ ɛ s ˌ k juː ˈ ɛ l / ("ess cue el"). Regardless, many English-speaking database professionals (including Donald Chamberlin himself ) use the acronym -like pronunciation of / ˈ s iː k w əl / ("sequel"), mirroring the language's prerelease development name, "SEQUEL". The SQL standard has gone through a number of revisions: The standard is commonly denoted by

1260-440: Was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Edgar F. Codd in the early 1970s. 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 Jose Research Laboratory had developed during

1296-627: Was later changed to SQL (dropping the vowels) because "SEQUEL" was a trademark of the UK-based Hawker Siddeley Dynamics Engineering Limited company. The label SQL later became the acronym for Structured Query Language. After testing SQL at customer test sites to determine the usefulness and practicality of the system, IBM began developing commercial products based on their System R prototype, including System/38 , SQL/DS , and IBM Db2 , which were commercially available in 1979, 1981, and 1983, respectively. In

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