Difference between select for update and lock in share mode for Row-level locks in MySQL

Record it by yourself to make a better impression. The English documents are from the official MySQL documents. The Chinese is translated by yourself according to your understanding.

Select... lock in share mode sets a Shared Mode Lock on the rows
Read. A Shared Mode Lock enables other sessions to read the rows
Not to modify them. The rows read are the latest available, so if they
Belong to another transaction that has not yet committed, the read
Blocks until that transaction ends.

Set a share mode lock on the read row. This shared lock allows other sessions to read data but cannot be modified. The row reads the latest data. If it is used by other transactions but not committed, the read lock will be blocked and the transaction ends.

Select... for update sets an exclusive lock on the rows
Read. An exclusive lock prevents other sessions from accessing the rows
For reading or writing.

Set an exclusive lock on the read row. Organize other sessions to read or write row data