Questions regarding inserting relation when using Upsert in Laravel - laravel

Question

At hourly basis I have a schedule running a job that connects to my bank and fetches my bank transactions.
Unfortunately, my bank's API return transactions without any transaction IDs, and also transaction details will change over time, example:
Once paying for something the transaction amount is only reserved from the account, not actually withdrawn. So if I pay $100, the amount is withdrawn from my account and a transaction item is created with the following details:
{
"amount": {
"amount": -100,
"currencyCode": "USD"
},
"accountingDate": "2021-01-19",
"description": "PAYMENT",
"transactionCode": "123",
"transactionType": null
}
And a few hours later, or even maybe up to a day, this transaction entry in the API will have changed to something like:
{
"amount": {
"amount": -100,
"currencyCode": "USD"
},
"accountingDate": "2021-01-19",
"description": "WALMART",
"transactionCode": "R_123",
"transactionType": "Purchase"
}
In this case it is three different values being changed: description, transactionCode and transactionType.
The description field gets updated with details of the vendor or receiver of the money.
The transactionCode field references the bank's transaction categorization (which is not public), but when the code is prefixed with R_ it means it's withdrawn and accounted.
The transactionType field is updated with information in regards of the type of transaction (not neccessary in correlation with the transactionCode field). Examples are "Visa", "Purchase", "Bill payment", "Fees", "Transfer between own accounts" etc.
So to handle this in my application I use the upsert function where I basically check for changes in any of the fields from the API which in 99% of the cases do work.
But; I thought I would extract the transactionCode values to a separate table, using them as categories in my own app. What is the quickest and easiest way to extract the data (regardless of its R_ prefix) with doing lots of queries to check the database for already existing value?
I'm thinking of something like for each transaction:
Get transactionCode value
Strip the R_ prefix
Check if transaction code exists in database
Insert if not
Create relation for transaction
But for several hundred transactions at a time it might not be suitable to do a check for each transaction code value. Would it make more sense to fetch all transaction codes before looping the transactions and then create the relations afterwards?
And also, how do I insert relation when using upsert?