SQL Server Common commands

To view the locked table:

Select request_session_id spid,object_name (resource_associated_entity_id) tableName
From sys.dm_tran_locks where resource_type= ' OBJECT '

SPID Lock Table Process
TableName Locked Table name

Unlock:

declare @spid int
Set @spid = 57--Lock table process
declare @sql varchar (+)
Set @sql = ' Kill ' +cast (@spid as varchar)
exec (@sql)

Lock table, Other transactions can read table, but cannot update delete

select * from table with (HOLDLOCK)  

lock table, Other transactions cannot read tables, update and delete  

SELECT * from table with (TABLOCKX)

Note: The difference between Holdlock and Tablockx.

###########################################################################################

SQL Server provides a powerful and complete locking mechanism to help achieve the concurrency and high performance of the database system. Users can use the default settings of SQL Server or use the lock options in the SELECT statement to achieve the desired effect. This article describes each of the "lock options" in the SELECT statement and the corresponding feature descriptions.


function Description:


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."


HOLDLOCK (Hold lock)


When this option is selected, SQL Server will persist this shared lock to the end of the entire transaction and will not be released on the way.


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.


Paglock (page lock)


This option is the default option when SQL Server uses a shared page lock when it is selected.


Tablockx (row it table lock)


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.

HOLDLOCK holds a shared lock until the entire transaction is complete and should be released immediately when the locked object is not needed, equal to the serializable transaction isolation level


NOLOCK statement execution does not emit a shared lock, allowing dirty reads, equal to the READ UNCOMMITTED transaction isolation level


paglock with multiple page locks where a table lock is used


READPAST Let SQL Server skip any locking lines, perform transactions, apply to READ UNCOMMITTED transaction isolation LEVEL only skip RID lock, skip page, zone and table lock


Rowlock forcing the use of row locks


Tablockx enforces exclusive table-level locks, which prevent any other transactions from using this table during a transaction


Uplock forcing updates to be used when reading tables without sharing locks

SQL Server Common commands