Updating multiple columns sql server
We can easily contrive for an “updates” table to exist by creating a temporary table and populating it.It is relatively straightforward to populate a table with multiple rows with just one query (or at least, far fewer queries than the number of rows desired).So if the caller has a Postgre SQL database, and calls with data to represent our third example (where the target values are all unique), then the Postgre SQL-specific subclass will effect the updates using the table / UPDATE … To match on names we now need to match on two columns.So whereas previously we specified the matching column using a scalar, when there is more than one column to match, we use an Array Ref.Also, let’s say we want to make updates only for people in the company “Widget Co”.“Bob Jones” appears in both companies, so we need to be careful to identify the company, but we don’t want to have to specify it repeatedly for each row.
A more effective solution to this problem is to attempt to reduce the number of UPDATE statements.
and we could persuade the database server to apply those updates to the target table?
This is in fact entirely possible in many database systems.
OK, that’s great, we have some theoretical approaches for reducing the number of queries, now what?
The code required to implement the above logic is sufficiently fiddly that we would probably not want to have to repeat it.