4D v16

primary_key_definition

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4D v16

4D SQL Reference

Syntax rules

primary_key_definition



	Command primary_key_definitio[CONSTRAINT sql_name] PRIMARY KEY (sql_name, ... , sql_name)

Description

A primary_key_definition is used to pass the column or combination of columns (sql_name) that will serve as the PRIMARY KEY (unique ID) for the table. The column(s) passed must not contain duplicate or NULL values.

An optional CONSTRAINT can also precede the PRIMARY KEY passed in order to limit the values that can be inserted into the column.

Example

This example creates a table and sets the SID column as the primary key:

CREATE TABLE Customer
(SID int32,
Last_Name varchar(30),
First_Name varchar(30),
PRIMARY KEY (SID));