Getting “ORA-01843: not a valid month” when calculating dates in SELECT

Question

I have the following view in Oracle

SELECT
1 as col1
,2 as col2

,CASE
     WHEN salesdata.date1 > '01/01/0001'
     THEN 24*60*(salesdata.date1 - salesdata.date2)
     ELSE NULL
   END      AS dateresult
FROM 
salesdata

I'm retrieving this view with a simple SELECT:

select * from viewsample

Then I run this line below:

OracleConnection connection = new OracleConnection(connectionString);
connection.Open();
DbCommand command = connection.CreateCommand();

command.CommandTimeout = 14400;
command.CommandText = sql;
DbDataReader reader = command.ExecuteReader(CommandBehavior.SingleRow);

When ASP.Net runs this line I get the error "ORA-01843: not a valid month".

It seems that the command understands the "dateresult" column as a DATE, but it is a INTEGER.

I've already tried a CAST like this and didn't work either:

CAST(24*60*(salesdata.date1 - salesdata.date2) as INTEGER)

Answer 1

You'll have to explicitly provide the date format of the string

to_date('01/01/0001','DD/MM/YYYY')

in the select. If not provided it uses the default setting on the client to do the implicit conversion to a date. The default date format is dependent on the regional settings of the client machine.