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التركية - الإنجليزية

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foreign key

A field in a relational database record that points to a key field in another table

An attribute that appears as a nonprimary key attribute in one entity and as a primary key attribute (or part of a primary key) in another entity

A column, or combination of columns, whose values must match those of a primary key in the same or different table A given foreign key value represents a reference from the row(s) containing it to the row containing the matching primary key value The problem of ensuring that every foreign key value does in fact match a value of the corresponding primary key is known as the referential integrity problem

A column, or set of columns, that references a unique or primary key in a different table

When a key in one table is referenced in another table, the key in the second table is called a foreign key (In the Students_Courses table in the diagram, the fields Soc_Sec_No and Course_ID are, respectively, foreign keys into the Students and Courses tables )

An item (or items) in one object that reference information in a primary key of another object; for example, the Region item in the DEALERS object is a foreign key because it references information in the Region_Code item (a primary key) in the STATES object See also Primary Key

The primary key of another (or the same) table which is repeated in a table to represent the correlation of both tables (e g Department number in an employees table)

A column in a table that does not uniquely identify rows in that table, but is used as a link to matching columns in other tables

A reference to another element within an element's definition

A column in a database table which is defined as a primary key in another table within the same database

An attribute added to an entity to create a relationship key This attribute is the primary key of the related entity

The primary key of one file or table which is implanted in another file or table to implement the relationships between them Foreign keys are used to implement some types of relationships Foreign keys do not exist in information models

In the context of ER diagrams, this is the field that helps an entity uniquely identify a "foreign" entity From the point of view of a corporation, the foreign key of a customer might be the customer number

An attribute in one table that is used to relate that tuple to a tuple in another table Example: a student table may contain an attribute called major code In the student table the major code is a foreign key because it allows us to relate that table to the major table where the major code is the primary key and contains the major name We could then print a list of students and their major names as a result of this foreign key/primary key relationship

A key used in one table to represent the value of a primary key in a related table While primary keys must contain unique values, foreign keys may have duplicates For instance, if we use student ID as the primary key in a Students table (each student has a unique ID), we could use student ID as a foreign key in a Courses table: as each student may do more than one course, the student ID field in the Courses table (often shortened to Courses student ID) will hold duplicate values

An attribute in a relation of a database that serves as the primary key of another relation in the same database See also Recursive foreign key

An attribute that appears as a nonprimary key attribute in one relation and as a primary key attribute (or part of a primary key) in another relation

One or more table attributes that can uniquely identify a record in another table A foreign key is the primary key of another table Foreign key-primary key relationships define a relational join See also relate

Column: cno References table COOP (cno)

(Concepts; search in this book)

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