Mass updating sql database

09-Feb-2020 03:37 by 3 Comments

Mass updating sql database - sim date dating

What I love about writing SQL Tuning articles is that I very rarely end up publishing the findings I set out to achieve. We have a table containing years worth of data, most of which is static; we are updating selected rows that were recently inserted and are still volatile. For the purposes of the test, we will assume that the target table of the update is arbitrarily large, and we want to avoid things like full-scans and index rebuilds.

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But we can group the updates according to the value being set, and then do one UPDATE statement per distinct value.

I include it here because it allows us to compare the cost of context-switches to the cost of updates.

DECLARE CURSOR c1 IS SELECT * FROM test6; rec_cur c1%rowtype; BEGIN OPEN c1; LOOP FETCH c1 INTO rec_cur; EXIT WHEN c1%notfound; UPDATE test SET fk = rec_, fill = rec_WHERE pk = rec_cur.pk; END LOOP; CLOSE C1; END; / This is the simplest PL/SQL method and very common in hand-coded PL/SQL applications.

It first performs UPDATE using INNER JOIN and then INSERTS all records that are not present in the table.

In this article I am populating the Grid View using the following XML file in the Page Load event.

Here are few tips to SQL Server Optimizing the updates on large data volumes. Let’s look at the execution plan of the query shown below.

In addition to the clustered index update, the index ix_col1 is also updated.The index can always be created once the update completes. Executing the update in smaller batches The query can be further optimized by executing it in smaller batches. The code below updates the records in batches of 20000. When updating in batches, even if the update fails or it needs to be stopped, only rows from the current batch are rolled back. Disabling Delete triggers Triggers with cursors can extremely slow down the performance of a delete query.Disabling After delete triggers will considerably increase the query performance. Replacing Update statement with a Bulk-Insert operation An update statement is a fully logged operation and thus it will certainly take considerable amount of time if millions of rows are to be updated.The first 4 records are already present in the Table, the only difference is that the countries of some records are modified for illustrating the bulk update operation.Here Mudassar Ahmed Khan has explained how to insert data from Excel sheet into SQL Server database table using Sql Bulk Copy in C# and VB. Sql Bulk Copy class as the name suggests does bulk insert from one source to another and hence all rows from the Excel sheet can be easily read and inserted using the Sql Bulk Copy class.Updating very large tables can be a time taking task and sometimes it might take hours to finish.

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