Querying MySql in SQL Server via openquery - "0000-00-00" rows not showing

Question

My setup is as follows. I have a MySQL database (5.5.34) which I linked to MS SQL via ODBC as "linked server" using MySQL ODBC 5.2 Driver.

MySQL query is as follows:

SELECT
CASE WHEN start = "0000-00-00" THEN NULL else start END as start,
CASE WHEN finish = "0000-00-00" THEN NULL else finish END as finish
FROM students

When run in phpmyadmin on the source server as a result I get a bunch of rows, some with dates and some with NULL in the start and/or finish columns. So far so good.

Now I try to put this into openquery and run the whole think from SQL Server via SQL Server Management Studio.

SELECT *    
FROM openquery(OLDSYSTEM, '
    SELECT
    CASE WHEN start = "0000-00-00" THEN NULL else start END as start,
    CASE WHEN finish = "0000-00-00" THEN NULL else finish END as finish
FROM students')

Now all the start and finish are null. I am baffled by this :/ If someone solved this problem before I would appreciate a hint.

Answer 1

It turns out that the problem was in the fact that MsSQL is able to store date in Date column that does not translate to date ie. 00 in month and/or 00 in day section.

In other words the dates we're all similar to 2014-12-00 or 2013-00-00 - I just haven't noticed.