Bind Variable : required - no message, not required - error

Question

hi
Please consider the example application created using JDeveloper 11.1.1.6.0
at http://www.consideringred.com/files/oracle/2012/RequiredOrNotBVarApp-v0.01.zip
It has these View Objects defined
- EmployeesReqNoValueBVarVO which has a required Bind Variable, and where clause "last_name like '%' || :LastNameBVar || '%'"
- EmployeesNotReqNoValueBVarVO which has a NOT required Bind Variable, and where clause "(:LastNameBVar is null or last_name like '%' || :LastNameBVar || '%')"
The Bind Variable in both View Objects does NOT have a value (no default value, not programmatically set, not entered by the user, ...).
This "no value set" aspect could be the result of a "development error", but the resulting observed behaviour is at least "peculiar".
- scenario (sc1) : run "try tryEmployeesReqNoValueBVarVO", see a table filled with rows and NO message about the required Bind Variable
- scenario (sc2) : run "try tryEmployeesNotReqNoValueBVarVO", see "No data to display." in the table and the "Missing IN or OUT parameter at index:: 1" error for the NOT required Bind Variable for a where clause that can deal with null values
- question (q1) How can be explained that scenario (sc1) does not result in an error message about the required Bind Variable (and scenario (sc2) does result in an error message about the NOT required Bind Variable)?
- question (q2) What does the "Required" checkbox for a Bind Variable really mean for Bind Variables used in a where clause of a View Object?
If the described behaviour can be reproduced (using RequiredOrNotBVarApp-v0.01.zip), confirmations are welcome.
(Aspects of these scenario's could be related to forum thread "Bind variable required/not required: strange behaviour".)
many thanks
Jan Vervecken

Answer 1

Thanks for your reply Frank.
Frank Nimphius wrote:
... your query actually is dependent on the existence of the bind variable because the bind variable is used in the where clause part. ...Sure, and the Bind Variable does exist (in both (sc1) and (sc2)).
... This has nothing to do with whether the bind variable value is checked for NULL and if the value it contains is NULL performs an "all you can eat" type of query. Because the existing, NOT required Bind Variable has not been given a value in scenario (sc2), the check for NULL only makes more explicit that NULL is a valid value for the SQL statement.
... Non required bind variables are used in the context of view criteria to avoid missing IN or OUT parameters. ...The "Required" checkbox for a Bind Variable is also available/enabled when the Bind Variable is not used in a View Criteria (in both (sc1) and (sc2)).
... In the case of a view criteria, the VO query may be executed without the view criteria applied and for this reason should not fail only because the defined bind variable is not provided. ...No View Criteria in the scenario's (sc1) and (sc2) I descirbe.
... If you run the query in the tester, you get
(java.sql.SQLException) Missing IN or OUT parameter at index:: 1
and no query is executed at all for EmployeesNotReqNoValueBVarVOSure, that matches scenario (sc2), but the Bind Variable can be configured as NOT required, how can it be missing?
The JDeveloper help page "Create or Edit Bind Variables Dialog - Variable Page" says:
"... Alternatively, you can use the SQL Statement page of the Edit View Objects dialog to enter a parameterized WHERE clause. Note that the bind variables you enter in a parameterized SQL WHERE clause will require a valid value at runtime or a runtime exception error will be thrown. ..."
So, null as a valid value, seems to explain the behaviour in scenario (sc1).
"... In contrast, when you create a view criteria filter condition that references a named bind variable, you can specify whether the value is required or optional. ..."
But, the "Required" checkbox is also available (to uncheck) for Bind Variables that are not used in a View Criteria.
Specifically for the "Required" checkbox the help page says : "... Select if you want to make the value of a name bind variable required for any usage the references the named bind variable. For example, when the value is required (default), all view criteria items that reference the named bind variable will fail to execute unless a valid value is supplied at runtime. Alternatively, you can leave the value not required and use the Create View Criteria dialog to specify whether or not individual view criteria items require the value. ..."
Again, the focus is on View Criteria, although it can also be unchecked (configuring as NOT Required) for Bind Variables that are not used in a View Criteria (which does not seem to be something you should do).
But, still, there is a perspective here that makes this possibly very confusing:
- a View Object where clause with a required Bind Variable, no value set --> results in rows, and NO message about a missing value
- a View Object where clause with a NOT required Bind Variable, no value set --> results in no rows, and a message about a missing value
regards
Jan