Advanced learning of MySQL -- Fundamentals -- concurrency of transactions

What problems will occur when transactions are concurrent :

Dirty reading

A transaction reads data that has not been committed by another transaction

Explain what ?
It means that neither transaction has been committed , The data read must be inaccurate , Non persistent data .

terms of settlement :
You can make transactions concurrent
But one of the slower transactions is before reading data , You must ensure that other concurrent transactions are committed , Otherwise, it is in a state of stagnation .
be called , Read submitted .( At this time, we found that , The problem of dirty reading has been solved )

It can't be read repeatedly

In a transaction , Read the same record successively , But the data read twice is different . Call it non repeatable .

Explain what ?
Explain the business ABC Concurrent , Business A Read the transaction B Data submitted , however A Still running , also A In subsequent operation , There is another operation of reading data , But this time I read it later is C Data submitted . here A I don't understand , How can the data read be inconsistent .

terms of settlement :
Do not allow transactions that process the same data to process the data at the same time , We have to wait for the previous transaction , To allow the next transaction to proceed .

Fantasy reading

When a transaction queries a record , There is no corresponding data , But when inserting , But I can't insert it , Found that this record exists .

Explain what ?
explain , When a transaction wants to insert data into a table , Mingming originally judged that this table did not have this row of data , But it was inserted in advance by another transaction , Cause insertion failure .

terms of settlement :
Transactions that operate on the same table are not concurrent .