mysql shared lock (S lock) and an exclusive lock (X lock)

　　mysql table level lock, and it can be divided into row-level locks. Here the record about row-level locking.

　　Check whether the database automatically submit the transaction:

. 1  - the ON to OFF to turn off 
2 Show Variables like  ' %% the autocommit '; 
. 3  - set to open automatically submit the transaction 
. 4  SET   the autocommit = . 1 ;
 . 5  - Set off automatically commit the transaction 
. 6  SET the autocommit =  0 ;

　　In the case of only two transactions have a lock with a shared lock (S-lock) will not cause obstruction.

　　

- MySQL shared locks on 
the SELECT ... Lock in report this content share the MODE;

- MySQL plus exclusive lock on 
the SELECT ... for  Update ;

- common query mechanism does not lock 
the SELECT ...;

　　As a transaction acquires an exclusive lock rows of data, other transactions can no longer acquire other locks of the line. (No locking mechanism can query or query.)