I have changed the @Id of a view from integer to varchar2(200). The CDT XSD had

From the Query Rule/Entity, are you able to retrieve data from the modified view?

You may have duplicate values for the id field. If the id field is not unique it will throw errors

Duplicate column gets created like A_id. Try deleting and recreating the view

The view's column which is mapped to the key/ID field should be distinct. Check its uniqueness.

try fetching data from query entity separately and if you are not able to do so. Please recreate your view and then try again. Please let us know if you face any further issues.

I have checked the View. There are no duplicate rows. We use the function sys_guid() to generate unique primary keys for different rows.

Testing with a Query Rule to fetch the data from DB, it fails.

The DataStore entity synchronized successfuly with the DB.

There error I am getting on the query rule is:
Expression evaluation error in rule 'test_accountcustomerview' at function 'queryruleexec': Error evaluating function 'queryruleexec' : Unexpected error executing query (type: [WMGGBLAccountCustomerViewDT56835], query: [test_AccountCustomerView], order by: [[]], filters:[null])

This is how I create it:

CREATE OR REPLACE FORCE VIEW "APPIAN_WMG_BD"."WMG_GBL_ACNT_CSTMR_VIEW"
SELECT
RAWTOHEX(sys_guid()) AS WMG_VIEW_ID,
.
.
.

Mohamedb,
If the only purpose of WMG_VIEW_ID is to have a primary key, just use ROW_ID.
I used the same thing and it worked. I am not sure of the data type you have mentioned in the CDT for this VIew ID.

@sanjays: That's what I was using in the begining, but the interface was very slow; so, we thought of trying with a different function sys_guid().

Concatenating data from different columns in a string can be an option, but again this approach is data dependent.

OK, there was a datatype mismatch between the XSD and the table.

When using the above mentioned SQL statement to generate a primary key on a DB View the following XSD representation for promary key works:

<xsd:element name="id" nillable="true" type="xsd:string">
<xsd:annotation>
<xsd:appinfo source="appian.jpa">@Id @GeneratedValue @Column(name="WMG_VIEW_ID", nullable=false, columnDefinition="VARCHAR2(200)")</xsd:appinfo>
</xsd:annotation>
</xsd:element>

Also, after updating the XSD, make sure to delete the entity from the datastore; and then re-map it again; then verify the DataStore mapping is worrking - so as to ensure that the DS has picked the latest XSD version.