SYSCONSTRAINTS

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SYSCONSTRAINTS

The sysconstraints system catalog table lists the constraints placed on the columns in each database table. An entry is also placed in the sysindexes system catalog table (or sysindices view for Dynamic Server) for each unique, primary key, NOT NULL, or referential constraint that does not already have a corresponding entry in sysindexes or sysindices. Because indexes can be shared, more than one constraint can be associated with an index. The sysconstraints table has the following columns.

Column	Type	Explanation
constrid	SERIAL	Code uniquely identifying the constraint
constrname	VARCHAR(128)	Name of the constraint
owner	VARCHAR(32)	Name of the owner of the constraint
tabid	INTEGER	Code uniquely identifying the table
constrtype	CHAR(1)	Code identifying the constraint type: C = Check constraint N = Not NULL P = Primary key R = Referential T = Table U = Unique
idxname	VARCHAR(128)	Name of index corresponding to constraint
collation (IDS)	CHAR(32)	Collating order at the time when the constraint was created.

A composite index on the constrname and owner columns allows only unique values. An index on the tabid column allows duplicate values, and an index on the constrid column allows only unique values.

For check constraints (where constrtype = C), the idxname is always NULL. Additional information about each check constraint is contained in the syschecks and syscoldepend system catalog tables.