Difference between revisions of "REFERENCES Column Constraint"
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==Purpose== | ==Purpose== | ||
Column constraint to create a relationship to an index key of another table | Column constraint to create a relationship to an index key of another table | ||
Revision as of 14:58, 29 October 2009
Purpose
Column constraint to create a relationship to an index key of another table
Syntax
REFERENCES <cTableName> [TAG <cTagName>]
See Also
ALTER TABLE, CONSTRAINTS, CREATE TABLE
Description
A constraint is used to define rules that help to provide data integrity. Column constraints are specific to the column name specified. You must have ALTER privilege on the table. The table will be locked for EXCLUSIVE use during the operation.
The REFERENCES column constraint is used to create a relationship to an index key of another table. The value of a column which has the REFERENCES column constraint set is validated by checking that it already exists as a value in the referenced index key.
The name of the referenced table is specified in <cTableName>. The index tag to reference is specified in <cTagName>. If the optional TAG <cTagName> clause is omitted, the primary index key of <cTableName> is used. If <cTableName> has no index tags, an error is generated.
Example
set sql to vfp CREATE TABLE supplier ; (SuppId i PRIMARY KEY, ; SuppName c(40) UNIQUE) CREATE TABLE purchase_order ; (POid i PRIMARY KEY, ; SuppId i REFERENCES supplier TAG SuppId, ; POtotal n(10,2) ) list dictionary
Products
Recital Database Server, Recital Mirage Server, Recital Terminal Developer
