Updating multiple rows at a time in sql server
Updating multiple rows at a time in sql server - 10 questions speed dating
I have a Table Products with a Trigger to create a record on each update made to Products (something like a Log).
But in many cases this only provides a modest improvement as each UPDATE operation still requires a round-trip communication with the database server.Microsoft is conducting an online survey to understand your opinion of the Msdn Web site.If you choose to participate, the online survey will be presented to you when you leave the Msdn Web site. Eventually every SET value is different, for example: UPDATE staff SET salary = 1125 WHERE name = ' Bob'; UPDATE staff SET salary = 1200 WHERE name = ' Jane'; UPDATE staff SET salary = 1100 WHERE name = ' Frank'; UPDATE staff SET salary = 1175 WHERE name = ' Susan'; UPDATE staff SET salary = 1150 WHERE name = ' John'; Since every SET clause is now different, we can’t coalesce any queries using the approaches mentioned before, so we still have one UPDATE statement for every row requiring changes. What if we had a database table which contained a representation of the updates we wanted to make, e.g.and we could persuade the database server to apply those updates to the target table?Consider the following code: The above code updates 10000 rows at a time and the loop continues till @@rowcount has a value greater than zero. Best practices while updating large tables in SQL Server1.
Always use a WHERE clause to limit the data that is to be updated2.Suppose you want to update a column with the value 0, if it that column contains negative value.Let us also assume that there are over 2 million row in that column that has a negative value. Top Speed desc, Time Sent desc ) as CD The #summary temporary table is creating summarised data about trips undertaken by a car. Driver from ( select Vehicle Id, Time Sent, Driver, Max(Top Speed), Max(Time Sent) from Car Data GROUP BY Vehicle Id, Time Sent, Driver ) as CD where CD. You may also want to read my article Find the Most Time Consuming Code in your SQL Server Database Madhivanan,an MSc computer Science graduate from Chennai-India, works as a works as a Lead Subject Matter Expert at a company that simplifies BIG data.