High-performance MySQL reading

1. Write operations in the transaction, four isolation levels, all add exclusive locks.

2. Read operations in the transaction, the first three isolation levels, no lock, the last isolation level, will be a shared lock.

3. The above write and read operations are implicitly added locks. You can display and lock read operations yourself: SELECT ... Lock in SHARE MODE (shared lock on this line of data); For UPDATE (this row of data is added to the lock)

4. Locks in a transaction are released at the same time, that is, the moment the transaction is committed or rolled back.

High-performance MySQL reading