How do you use the table hint TABLOCK in a SQL Query?

Here is a query that updates a value in the Northwind Shippers table using TABLOCK:
----------
Use Northwind
GO
UPDATE  Shippers
WITH (TABLOCK)
SET CompanyName='Speedy Gonsalez'
WHERE ShipperID=1
--
SELECT * from Shippers
------------
The query updates the name of the shipping company whose ID=1 to a new name. When TABLOCK is used in the above manner it should be within the parenthesis.

Read this recommendation from Microsoft:

"An UPDATE statement always acquires an exclusive (X) lock on the table it modifies, and holds that lock until the transaction completes. With an exclusive lock, no other transactions can modify data. You can specify table hints to override this default behavior for the duration of the UPDATE statement by specifying another locking method, however, we recommend that hints be used only as a last resort by experienced developers and database administrators"

TABLOCK is one of several table hints in SQL Server which includes the following:

   FORCESCAN 
   FORCESEEK 
   HOLDLOCK  
   NOLOCK  
   NOWAIT 
   PAGLOCK  
   READCOMMITTED  
   READCOMMITTEDLOCK  
   READPAST  
   READUNCOMMITTED  
   REPEATABLEREAD  
   ROWLOCK  
   SERIALIZABLE  
   SNAPSHOT  
   SPATIAL_WINDOW_MAX_CELLS = integer 
   TABLOCK  
   TABLOCKX  
   UPDLOCK  
   XLOCK 

Table hints can be used with any of the following operations:
Applies to:
DELETE
INSERT
SELECT
UPDATE
MERGE

What is a Common Table Expression (CTE) in SQL Server?

Microsoft documentation defines Common Table Expression thus,

"A common table expression (CTE) can be thought of as a temporary result set that is defined within the execution scope of a single SELECT, INSERT, UPDATE, DELETE, or CREATE VIEW statement. A CTE is similar to a derived table in that it is not stored as an object and lasts only for the duration of the query. Unlike a derived table, a CTE can be self-referencing and can be referenced multiple times in the same query.

It is unlike a temporary table (persisted) during a connection or a view persisted in the database. CTE is only in memory.

We will consider CTE's many use case scenarios in later posts and the objective of this post is to give a simple example using the Northwind database.

A CTE should have the following:

• CTE with a CTE Expression name
• An Optional Column list
• A query defining the CTE

After a CTE is defined it can be referenced like a table or view and you can do all of the following statements:

• Select
• Insert
• Update
• Delete

It can also be used in defining a view by providing the columns.

Now let me define CTE using the Employees table in Northwind. The example is just to show the syntax as the result can be obtained from a single query without using CTE.

USE Northwind
Go
---define the common table expression
WITH NEmp_CTE (FirstName,LastName,CITY)  /*Name: Nemp_CTE, Column List:FirstName, LastName,City*/
AS
---define the CTE query
(SELECT FirstName,LastName,City
from Employees
where City in ('Tacoma','London')
)
---Use it in a Select Query
SELECT LastName,FirstName,CITY
From NEmp_CTE
where LastName <>'Buchanan'
go

The response to this query is:

Note: The response such as the above does not really need a Common Table Expression but the point was to show the construction of the Syntax used for CTE. In fact, it is to make complex queries more readable.