Building the Action Diagram › How to Define Logic for Elementary Processes and Procedures › Add Entity Actions › Create Entity Actions in the Action Diagram › READ or CREATE Entity

READ or CREATE Entity

You must READ or CREATE an entity before you UPDATE it. It is also possible for the view being acted upon to be a persistent view READ or CREATEd by an earlier action block.

When using an UPDATE statement, add appropriate READ and CREATE entity actions to the Action Diagram. Use SET to change attribute values.

The UPDATE action statement has the following format:

UPDATE entity-view-1
[SET attribute-view-1 TO expression ] ...
[REMOVE attribute-view-2]...
[ASSOCIATE WITH entity-view-2 WHICH relationship IT]...
[DISASSOCIATE FROM entity-view-3 WHICH relationship-2 IT]...
[TRANSFER FROM entity-view-4 WHICH relationship-3 IT
TO entity-view-4 WHICH relationship-4 IT]...
WHEN successful
action-statement-list
WHEN not unique
action-statement-list

Downstream Effects: The generated code eliminates the need to search the DBMS for a record to be UPDATEd when the following conditions occur:

• The table being UPDATEd has been READ successfully
• The table is not involved in another READ or CREATE
• The READ and the UPDATE use the same view
• The view is not used in any other READ statement except with WHERE conditions
• The WHERE CURRENT on the cursor name can be used because the cursor is already positioned on the row requiring the update.