Sql UPDATE
Section 19.1: UPDATE with data from another table
The examples below fill in a PhoneNumber for any Employee who is also a Customer and currently does not have a phone number set in the Employees Table.
(These examples use the Employees and Customers tables from the Example Databases.)
Standard SQL
Update using a correlated subquery:
UPDATE
Employees
SET PhoneNumber =
(SELECT
c.PhoneNumber
FROM
Customers c
WHERE
c.FName = Employees.FName
AND c.LName = Employees.LName)
WHERE Employees.PhoneNumber IS NULL
SQL:2003
Update using MERGE:
MERGE INTO
Employees e
USING
Customers c
ON
e.FName = c.Fname
AND e.LName = c.LName
AND e.PhoneNumber IS NULL
WHEN MATCHED THEN
UPDATE
SET PhoneNumber = c.PhoneNumber
SQL Server
Update using INNER JOIN:
UPDATE
Employees
SET
PhoneNumber = c.PhoneNumber
FROM
Employees e
INNER JOIN Customers c
ON e.FName = c.FName
AND e.LName = c.LName
WHERE
PhoneNumber IS NULL
Modifying existing values
This example uses the Cars Table from the Example Databases.
UPDATE Cars
SET TotalCost = TotalCost + 100
WHERE Id = 3 or Id = 4
Update operations can include current values in the updated row. In this simple example the TotalCost is incremented by 100 for two rows:
- The TotalCost of Car #3 is increased from 100 to 200
- The TotalCost of Car #4 is increased from 1254 to 1354
A column's new value may be derived from its previous value or from any other column's value in the same table or a joined table.
Updating Specified Rows
This example uses the Cars Table from the Example Databases.
UPDATE
Cars
SET
Status = 'READY'
WHERE
Id = 4
This statement will set the status of the row of 'Cars' with id 4 to "READY".
WHERE clause contains a logical expression which is evaluated for each row. If a row fulfills the criteria, its value is updated. Otherwise, a row remains unchanged.
Updating All Rows
This example uses the Cars Table from the Example Databases.
UPDATE Cars
SET Status = 'READY'
This statement will set the 'status' column of all rows of the 'Cars' table to "READY" because it does not have a WHERE clause to filter the set of rows.
Capturing Updated records
Sometimes one wants to capture the records that have just been updated.
CREATE TABLE #TempUpdated(ID INT)
Update TableName SET Col1 = 42
OUTPUT inserted.ID INTO #TempUpdated
WHERE Id > 50
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