.ql

Information about .ql

**.QL**

Paradigm:	multi-paradigm,logic-paradigm,object-oriented-paradigm
Appeared in:	2007
Developer:	Semmle
Typing discipline:	static, strong
Major implementations:	SemmleCode

.QL [ˈdotˈkjuˈɛl] is an object-oriented query language used to retrieve data from relational database management systems. It has flavours of a standard query language SQL and an object-oriented programming language Java. .QL is an object-oriented variant of the logic programming language, known in the databases community as Datalog. Hierarchical data can therefore be naturally queried in .QL in recursive manner.

Queries written in .QL are optimised, compiled into SQL and can then be executed in any major relational database management system. .QL query language is being used in SemmleCode to query a relational representation of Java programs.

.QL is developed at Semmle Limited and is based on the company's proprietary technology.

Language Features

.QL has several language features to make queries concise, intuitive and reusable:

Extensible type hierarchy
Methods and predicates
Definition before use

Example query

The sample query below illustrates use of .QL to query a Java program. This is how one would select all classes that contain more than ten public methods: from Class c, int numofm where numofm = count(Method m| m.getDeclaringType()=c and m.hasModifier("public")) and numofm > 10 select c.getPackage(), c, numofm In fact, this query selects not only all classes with more than ten public methods, but also their corresponding packages and the number of methods each class has.

References

Hervé Gallaire and Jack Minker. Logic and Databases. Plenum Press, New York,1978.
Serge Abiteboul and Paris C. Kanellakis. Object identity as a query language primitive. In SIGMOD Rec, pages 159-173, ACM Press, 1989.
Oege de Moor, Elnar Hajiyev and Mathieu Verbaere. Object-oriented queries over software systems. In proceedings of the 2007 ACM SIGPLAN symposium on Partial evaluation and semantics-based program manipulation, page 91, ACM Press, 2007.

External links

.QL language reference
Semmle Limited creators of .QL

Topics in database management systems (DBMS) • • [ edit]
Concepts Database Database models Database storage Relational model Distributed DBMS ACID Null Relational database Relational algebra Relational calculus Database normalization Referential integrity Relational DBMS Primary key, Foreign key, Surrogate key, Superkey, Candidate key
Objects Trigger View Table Cursor Log Transaction Index Stored procedure Partition	Topics in SQL Select Insert Update Merge Delete Join Union Create Drop Begin work Commit Rollback Truncate Alter
Implementations of database management systems
Types of implementations Relational Flat file Deductive Dimensional Hierarchical Object oriented Object relational Temporal XML data stores
Database products Object-oriented (comparison) Relational (comparison)	Components Query language Query optimizer Query plan ODBC JDBC

A programming paradigm is a fundamental style of programming regarding how solutions to problems are to be formulated in a programming language. (Compare with a methodology, which is a style of solving specific software engineering problems).
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A multiparadigm programming language is a programming language that supports more than one programming paradigm. As Leda designer Tim Budd holds it: The idea of a multiparadigm language is to provide a framework in which programmers can work in a variety of styles, freely
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<noinclude></noinclude> Logic programming (which might better be called logical programming by analogy with mathematical programming and linear programming) is, in its broadest sense, the use of mathematical logic for computer programming.
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An object-oriented programming language (also called an OO language) is one that allows or encourages, to some degree, object-oriented programming techniques such as encapsulation, inheritance, interfaces, and polymorphism.
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A software developer is a person who is concerned with one or more facets of the software development process, a somewhat broader scope of computer programming or a specialty of project managing.
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In computer science, a type system defines how a programming language classifies values and expressions into types, how it can manipulate those types and how they interact.
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In computer science and computer programming, the term strong typing is used to describe those situations where programming languages specify one or more restrictions on how operations involving values having different datatypes can be intermixed.
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Implementation is the realization of an application, or execution of a plan, idea, model, design, specification, standard, algorithm, or policy.

In computer science, an implementation is a realization of a technical specification or algorithm as a program, software
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SemmleCode is a tool for improving the quality of computer software. It can be used to find programming bug patterns, to compute software metrics, and to enforce coding conventions. All these tasks can be formulated as queries in an object-oriented query language named .QL.
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A database management system (DBMS) is computer software designed for the purpose of managing databases. Typical examples of DBMSs include Oracle, DB2, Microsoft Access, Microsoft SQL Server, PostgreSQL, MySQL, FileMaker and Sybase Adaptive Server Enterprise.
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SQL
Paradigm: multi-paradigm
Appeared in: 1974
Designed by: Donald D. Chamberlin and Raymond F. Boyce
Developer: IBM
Latest release: SQL:2003/ 2003
Typing discipline: static, strong
Major implementations: Many
SQL
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Java

Paradigm: Object-oriented, structured, imperative
Appeared in: 1995
Designed by: Sun Microsystems
Typing discipline: Static, strong, safe, nominative
Major implementations: Numerous
Influenced by: Objective-C, C++, Smalltalk, Eiffel,^[1]
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Datalog is a query and rule language for deductive databases that syntactically is a subset of Prolog. Its origins date back to the beginning of logic programming, but it became prominent as a separate area around 1978 when Hervé Gallaire and Jack Minker organized a workshop on
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database is a structured collection of records or data that is stored in a computer system so that a computer program or person using a query language can consult it to answer queries. The records retrieved in answer to queries are information that can be used to make decisions.
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A data model is not just a way of structuring data: it also defines a set of operations that can be performed on the data. The relational model, for example, defines operations such as select, project, and join.
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flat file database describes any of various means to encode a data model (most commonly a table) as a plain text file.

Unordered

Unordered storage typically stores the records in the order they are inserted, while having
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The relational model for database management is a database model based on predicate logic and set theory. It was first formulated and proposed in 1969 by Edgar Codd with aims that included avoiding, without loss of completeness, the need to write computer programs to
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A distributed database management system is a software system that permits the management of a distributed database and makes the distribution transparent to the users. A distributed database is a collection of multiple, logically interrelated databases distributed over a computer network.
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ACID (Atomicity, Consistency, Isolation, Durability) is a set of properties that guarantee that database transactions are processed reliably. In the context of databases, a single logical operation on the data is called a transaction.
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Null is a special marker used to indicate that a data value is unknown in the Structured Query Language (SQL). Introduced by the creator of the relational database model, Dr. E.F.
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A relational database is a database that conforms to the relational model, and refers to a database's data and schema (the database's structure of how that data is arranged).
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Relational algebra, an offshoot of first-order logic, is a set of relations closed under operators. Operators operate on one or more relations to yield a relation. Relational algebra is a part of computer science.
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The relational calculus refers to the two calculi, the tuple relational calculus and the domain relational calculus, that are part of the relational model for databases and that provide a declarative way to specify database queries.
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