Locks in SQL Server

NOLOCK (without lock)

When this option is selected, SQL Server does not add any locks when reading or modifying data. In this case, it is possible for the user to read the data in the incomplete transaction (uncommited Transaction) or rollback (roll back), known as "dirty data."

UPDLOCK (Modify Lock)
When this option is selected, SQL Server uses a modify lock instead of a shared lock when reading data, and holds the lock to the entire transaction or to the end of the command. Using this option ensures that multiple processes can read data at the same time, but only that process can modify the data.

TABLOCK (table Lock)
When this option is selected, SQL Server will place a shared lock on the entire table until the command ends. This option ensures that other processes can read only and cannot modify the data.

TABLOCKX (exclusive table Lock) (indicates that no other process can read, not modify)
When this option is selected, SQL Server will place an exclusive lock on the entire table until the command or transaction ends. This prevents other processes from reading or modifying the data in the table

This lock prevents any other transactions from using this table during a transaction

Locks in SQL Server