APEX

KatReed wrote:

I am currently working in Oracle Application Express 18.1.0.00.45 and I am getting an error that I do not understand.

I created an interactive grid using the following query:

select periodic_topics_id, filter, topic, CASE WHEN LINK1 like '%116%' then LINK1||:APP_SESSION ELSE LINK1 END AS LINK1 From periodic_topics where meeting like :P31_MEETING_DESC and (nvl(:P31_FILTER,'0') = '0' or instr(:P31_FILTER||':',filter||':') > 0) 

In the table in the database, the periodic_topics_id column is the primary key and it is automatically populated when a new row is added to the table using the following trigger:

create or replace TRIGGER periodic_topics_trigger BEFORE INSERT ON periodic_topics FOR EACH ROW BEGIN :new.periodic_topics_id := periodic_topics_seq.nextval; END;

In the APEX application, link1 is a textfield and in the "Link" section of this column's properties, the "Target" is of type URL and the URL is &LINK1. I also indicated in the APEX application that periodic_topics_id is the primary key. These are the properties of the link column that I am referring to:

The problem: when I manually insert a value into a cell in the "LINK1" column of the interactive grid, an error is raised that says:

"•Ajax call returned server error ORA-20987: APEX - Process 'Periodic Topics - Save Interactive Grid Data' raised 'ORA-01733: virtual column not allowed here' while executing a DML command. This error can occur if a column is based on an aggregation or SQL expression. Set column attribute 'Query Only' to Yes to exclude the column from the INSERT and UPDATE statement. - Contact your application administrator. for ."

However, if I create the interactive grid using the same query but without the case statement, then I have no problem adding a link in the interactive grid. No error occurs. In other words, no error occurs when I try to add a value to the "Link1" column in the interactive grid if I create the interactive grid using the following query:

select periodic_topics_id, filter, topic, link1 From periodic_topics where meeting like :P31_MEETING_DESC and (nvl(:P31_FILTER,'0') = '0' or instr(:P31_FILTER||':',filter||':') > 0)

Just FYI, I need the query to have the case statement because some of the links will direct the user to external websites and others will direct the user to another page in the application. Without the case statement concatenating :APP_SESSION to the link, the user is forced to log back in to the application whenever they click on a link that directs them to another page in the application.

Does anyone know why the error would occur when the case statement is in the query but not when the case statement isn't in the query?

The error is occurring because the case expression does indeed turn LINK1 into a virtual column. Oracle cannot use the LINK1 column in DML operations because it is sourced from an expression, not a column name.

There is a simple fix.

1. Change the IG source query to:

select periodic_topics_id, filter, topic, link1

From periodic_topics

where meeting like :P31_MEETING_DESC

and (nvl(:P31_FILTER,'0') = '0' or instr(:P31_FILTER||':',filter||':') > 0)

2. Manually add a column to the grid (Ctrl+Click on the Columns node in Page Designer and select Create Column).

3. Set the following properties on the new column:

Name: LINK_SESSION

Type: Hidden

Source Type: SQL Expression

SQL Expression:

case

when link1 like '%116%' then :app_session

else null

end

4. Change the link Target on the LINK1 column to &LINK1.&LINK_SESSION.

However this is not a robust solution:

• What if the application ID has to change?
• What if a user pastes in an external URL that coincidentally includes the characters "116"?
• What if a ":" is missed from the end of an internal URL?