I have dates in the format of 06-02-2019
Unwritten Rule of Databases - Dates have no format.
Not any that you or I need to worry about, anyway.
BTW; When is "06-02-2019"? June 2nd or the 6th of February?
The ordering rules for Strings and Dates are [very] different.
As we all know
31/12/2018 < 01/01/2019
"31/12/2018" > "01/01/2019" (because "3" > "0")
If you want to do "date" things with a field then it really, really ought to be a Date field. Trying to do anything else is just asking for trouble. Trying to do any sort of conversion "on the fly" is problematic ("dodgy" data loses data or breaks the query completely) and will be slow, having to run the conversion function on each and every row in the table (i.e. table-scanning!).