1. The client sends the statement to the server for execution.
2. Query cache.
3. Statement validity check.
4. Language meaning check ( column name or table name error ).
5. Obtain the object parsing lock
6. Verification of data access rights
7. Determine the best execution plan. The server process will optimize this statement according to certain rules.
8. Statement parsing statement execution. Statement execution is also divided into two cases.One is that if the data block where the selected row is located has been read into the data buffer, the server process will directly pass the data to the client. Second, if the data is not in the buffer, the server process will query the relevant data from the database file and put the data into the data buffer.
9. Extract data. In the server-side process, there is a piece of code that is responsible for data extraction, andreturns the queried data results to the user-side process