Currency code to be changed for a purchase requistion which is in closed state

Hello Team,

We have purchase requistion which was created by mistake with domestic currency (SAR to SAR) instead of foreign currency, but the PO amount is correct only and is in closed status.

We just want to change the currency flag from SAR to EUR (like its foreign PO) since the PO amount value is having correct value.

What fields to be modified to have this change in purchase requisition by using SQL? Any help will be appreciated.

Note: I know Oracle doesn't support SQL updates, but if you guys can suggest the flags to be updated, we will take action accordingly.