I understand this, but I'm talking about absolutely different transaction with the same txid because it's possible due to collisions cause it's not possible that every transaction will have the absolutely unique txid.
Right now it is not possible to have two different transactions with same transaction ID although this collision had actually happen to the Coinbase Transaction (first transaction) but currently BIP 30 prevents a block from a transaction ID of an already existing transaction. Before this improvement it could have been possible to have same ID and it’s effect is having your transaction unspendable.
You can read it up here
https://github.com/bitcoin/bips/blob/master/bip-0030.mediawiki