I have the following SQL-code in my (SAP IdM) Application:
Select mcmskeyvalue as MKV,v1.searchvalue as STARTDATE, v2.avalue as Running_Changes_flag
from idmv_entry_simple
inner join idmv_value_basic_active v1 on mskey = mcmskey and attrname = 'Start_of_company_change'
and mcentrytype = 'MX_PERSON' and to_date(v1.searchvalue,'YYYY-MM-DD')<= sysdate+3
left join idmv_value_basic v2 on v2.mskey = mcmskey and v2.attrname = 'Running_Changes_flag'
where mcmskey not in (Select mskey from idmv_value_basic_active where attrname = 'Company_change_running_flag')
I already found the solution for the ORA-01841 problem, as it could either be a solution similar to MSSQLs try_to_date as mentioned here: How to handle to_date exceptions in a SELECT statment to ignore those rows?
or a solution where I change the code to something like this, to work soly on strings:
Select mcmskeyvalue as MKV,v1.searchvalue as STARTDATE, v2.avalue as Running_Changes_flag
from idmv_entry_simple
inner join idmv_value_basic_active v1 on mskey = mcmskey and attrname = 'Start_of_company_change'
and mcentrytype = 'MX_PERSON' and v1.searchvalue<= to_char(sysdate+3,'YYYY-MM-DD')
left join idmv_value_basic v2 on v2.mskey = mcmskey and v2.attrname = 'Running_Changes_flag'
where mcmskey not in (Select mskey from idmv_value_basic_active where attrname = 'Company_change_running_flag')
So for the actually problem I have a solution.
But now I came into discussion with my customers and teammates why the error happens at all.
Basically for all entries of idmv_value_basic_activ that comply to the requirement of "attrname = 'Start_of_company_change'" we can be sure that those are dates. In addition, if we execute the query to check all values that would be delivered, all are in a valid format.
I learned in university that the DB-Engine could decide in which order it will run individual segments of a query. So for me the most logical explanation would be that, on the development environment (where we face the problem), the section " to_date(v1.searchvalue,'YYYY-MM-DD')<= sysdate+3” is executed before the section “attrname = 'Start_of_company_change'”
Whereas on the productive environment, where everything works like a charm, the segments are executed in the order that is descripted by the SQL Statement.
Now my Question is:
First: do I remember that right, since the teacher said that only once and at that time I could not really make sense out of it
And Second: Is this assumption of mine correct or is there another reason for the problem?
Borderinformation:
The Tool uses a kind of shifted data structure which is why there can be quite a few different types in the actual “Searchvalue” column of the idmv_value_basic_activ view. The datatype on the database layer is always a varchar one.
"the DB-Engine could decide in which order it will run individual segments of a query"
This is correct. A SQL query is just a description of the data you want and where it's stored. Oracle will calculate an execution plan to retrieve that data as best it can. That plan will vary based on any number of factors, like the number of actual rows in the table and the presence of indexes, so it will vary from environment to environment.
So it sounds like you have an invalid date somewhere in your table, so to_date raises an exception. You can use validate_conversion to find it.