Clarion Community Help

This page is read only. You can view the source, but not change it. Ask your administrator if you think this is wrong.

| **Navigation:**  [[introduction.htm|Language Reference]] > 5 - Declaration Attributes > Variable and Entity Attributes >====== PRIMARY (set relational primary key) ====== | [[pre  set label prefix .htm|{{btn_prev_n.gif|Previous page}}]][[introduction.htm|{{btn_home_n.gif|Return to chapter overview}}]][[private  set variable private to a class module .htm|{{btn_next_n.gif|Next page}}]] |
|  ||

**PRIMARY**

{{blk2blue.jpg|blk2blue.jpg}}

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]]