UNIQUE Column Constraint

Purpose

Column constraint to define a candidate index for a table

Syntax

UNIQUE [COLLATE <cCollateSequence>]

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 UNIQUE column constraint is used to define the column as a candidate index for the table. A unique tag index is built on the specified column; it is given the same name as the column. More than one column can be defined as a candidate index for the table.

The optional COLLATE <cCollateSequence> clause is included for Visual FoxPro language compatibility only.

Example

CREATE TABLE newcust;
  (acc_ref char(5) default strzero(seqno(),5) UNIQUE,;
  acc_name char(20) UNIQUE)

Products

Lianja, Lianja Server