Access update query where clause

After the execution of the update from a select query the output of the Persons table will be as shown below;. After the SET keyword, we specified the column names to be updated, and also, we matched them with the referenced table columns.

After the FROM clause, we retyped the table name, which will be updated. In addition to this, we can specify a WHERE clause and filter any columns of the referenced or updated table.

We can also rewrite the query by using aliases for tables. Indexes are very helpful database objects to improve query performance in SQL Server. Particularly, if we are working on the performance of the update query, we should take into account of this probability. The following execution plan illustrates an execution plan of the previous query.

The only difference is that this query updated the 3. This query was completed within 68 seconds. We added a non-clustered index on Persons table before to update and the added index involves the PersonCityName and PersonPostCode columns as the index key. The following execution plan is demonstrating an execution plan of the same query, but this query was completed within seconds because of the added index, unlike the first one.

We have seen this obvious performance difference between the same query because of index usage on the updated columns. As a result, if the updated columns are being used by the indexes, like this, for example, the query performance might be affected negatively.

In particular, we should consider this problem if we will update a large number of rows. To overcome this issue, we can disable or remove the index before executing the update query. On the other hand, a warning sign is seen on the Sort operator, and it indicates something does not go well for this operator.

Post as a guest Name. Email Required, but never shown. The Overflow Blog. Stack Gives Back Safety in numbers: crowdsourcing data on nefarious IP addresses. Featured on Meta. New post summary designs on greatest hits now, everywhere else eventually. Visit chat. Related Hot Network Questions. You can change several fields at the same time.

The following example increases the Order Amount values by 10 percent and the Freight values by 3 percent for shippers in the United Kingdom:. This example changes values in the ReportsTo field to 5 for all employee records that currently have ReportsTo values of 2. Skip to main content. Toggle navigation. Products Microsoft Access Products. All Microsoft Access Products. Total Access Admin. Total Visual Agent. Total Access Analyzer. Total Visual CodeTools.

Total Access Components. Total Access Detective. Total Access Memo. Total Visual SourceBook. Total Access Speller. Total Access Startup. Total Access Statistics. Multi-Product Suites. Total Access Ultimate Suite. Total Access Developer Suite. Total Visual Developer Suite. Visual Basic 6 Products. Total VB Statistics. Total VB Enterprise Suite. Other Products.