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**PRIMARY**

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The **PRIMARY** attribute (PROP:PRIMARY) specifies the KEY is unique, includes all records in the file, and does not allow "null" values in any of the fields comprising the KEY. This is the definition of a file's "Primary Key" per the relational database theory as expressed by E. F. Codd.

**Example:**

**Names   FILE,DRIVER('TopSpeed'),PRE(Nam)   !Declare a file structure**

**NameKey   KEY(Nam:Name),OPT                !Declare name key, exclude blanks**

**NbrKey    KEY(Nam:Number),****PRIMARY****            !Declare number key as the primary key**

**Rec        RECORD**

**Name        STRING(20)**

**Number      SHORT**

**           END**

**       END**

**See Also:**

[[key  declare dynamic file access index .htm|KEY]]