Find function TO_DATE oracle in QGIS

In QGIS I get an error (to_date function error), can you tell me why?`

If it’s impossible, what can we replace it with?

TO_DATE(t.DATE_TOURNEE,'DD/MM/YYYY') as DATE_TOURNEE  

Answer

Please use below function,

to_date(substr(t.DATE_TOURNEE, 0, instr(t.DATE_TOURNEE, '.')-1), 'YYYY-MM-DD"T"hh24: mi: ss') 

Demo https://dbfiddle.uk/?rdbms=oracle_11.2&fiddle=f595387b2bc649dbf1a07453a0593baf