Database Toolbox

crossreference

Get information about primary and foreign keys

Syntax

f = crossreference(dbmeta, 'pcata', 'psch', 'ptab', 'fcata', 'fsch', 
'ftab')

Description

f = crossreference(dbmeta, 'pcata', 'psch', 'ptab', 'fcata', 'fsch', 'ftab') returns information about the relationship between foreign keys and primary keys. Specifically, the information is for the database whose database metadata object is dbmeta, where dbmeta was created using dmd. The primary key information is for the table ptab, in the primary schema psch, of the primary catalog pcata. The foreign key information is for the foreign table ftab, in the foreign schema fsch, of the foreign catalog fcata.

Examples

Type

f = crossreference(dbmeta,'orcl','SCOTT','DEPT',...
    'orcl','SCOTT','EMP')

MATLAB returns

f = 
Columns 1 through 7
    'orcl'   'SCOTT'   'DEPT'   'DEPTNO'    'orcl'    'SCOTT'    'EMP'
Columns 8 through 13
    'DEPTNO'    '1'    'null'    '1'    'FK_DEPTNO'    'PK_DEPT' 

In this example:

• dbmeta is the database metadata object
• orcl is the catalog pcata and the catalog fcata
• SCOTT is the schema psch and the schema fsch
• DEPT is the table ptab that contains the referenced primary key
• EMP is the table ftab that contains the foreign key

The results show the primary and foreign key information

Column	Description	Value
1	Catalog containing primary key, referenced by foreign imported key	orcl
2	Schema containing primary key, referenced by foreign imported key	SCOTT
3	Table containing primary key, referenced by foreign imported key	DEPT
4	Column name of primary key, referenced by foreign imported key	DEPTNO
5	Catalog that has foreign key	orcl
6	Schema that has foreign key	SCOTT
7	Table that has foreign key	EMP
8	Foreign key column name, that is the column name that references the primary key in another table	DEPTNO
9	Sequence number within foreign key	1
10	Update rule, that is, what happens to the foreign key when the primary key is updated.	null
11	Delete rule, that is, what happens to the foreign key when the primary key is deleted.	1
12	Foreign imported key name	FK_DEPTNO
13	Primary key name in referenced table	PK_DEPT

.

In the schema SCOTT, there is only one foreign key. The table DEPT contains a primary key DEPTNO that is referenced by the field DEPTNO in the table EMP. DEPTNO in the EMP table is a foreign key.

For a description of the codes for update and delete rules, see
http://java.sun.com/products/jdk/1.2/docs/api/java/sql/package-summary.html for the DatabaseMetaData object property getCrossReference.

See Also
dmd, exportedkeys, get, importedkeys, primarykeys

confds

database