Update select sum sql server

I have another question After creating a table and finishing 10 different UPDATE in a order, if I then found one update needs to be fixed, do I need to re-run the whole table and all other 9 updates?

But SQL does not allow me to usesum function in update. On 4 Feb , gooday wrote: Thanks Hugo, that is a great help! Hi gooday, I'm not sure what you mean.

See www. If for example the fifth UPDATE is the one that went wrong, the sixth and seventh don't use any data changed by the fifth, but the eighth does and the ninth and tenth use columns affected by the eigtht, then you should probably rerun the fifth after correcting it!

To be sure, you'd need to carefully inspect what each update statement does and how each statement affects the statements that follow it. Erland Sommarskog. There might be, but not seeing your query it's a bit too much of a dark room to tell where the light switch might be.

Even more difficult to tell. If not, no. This discussion thread is closed Start new discussion. Similar topics Oracle Database. PostgreSQL Database. DB2 Database. Mostly, we use constant values to change the data, such as the following structures. The full update statement is used to change the whole table data with the same value.

This type of update statement is a bit complicated than the usual structures. In the following sections, we will learn how to write this type of update query with different methods, but at first, we have to prepare our sample data. With the help of the following query, we will create Persons and AddressList tables and populate them with some synthetic data. These two tables have a relationship through the PersonId column, meaning that, in these two tables, the PersonId column value represents the same person.

In this method, the table to be updated will be joined with the reference secondary table that contains new row values. So that, we can access the matched data of the reference table based on the specified join type. Lastly, the columns to be updated can be matched with referenced columns and the update process changes these column values.

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.

You should then make it a derived table and move it to the FROM statement of the outer query. All right - what was my emergency again?

You must be logged in to reply to this topic. Login to reply. April 1, at am That would help alot. April 2, at am If through testing it becomes clear that the performance is inadequate, consider alternative query forms.