Bangkok web cam sex - Updating multiple tables sql server

So, given a list of updates to apply we could effect them using the following steps: So in the example above we can reduce five statements to four. But now the number of statements is no longer directly dependent on the number of rows requiring updates.

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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.

In the case of Postgre SQL, it can be done using a FROM clause with UPDATE, like this: This does an INNER JOIN between the tables “staff” and “updates” where the column “name” matches.

The SET clause then takes the “salary” field from the “updates” table and uses it to update the “salary” field of the “staff” table.

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.

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.

If there is no database-specific subclass for the database in use, then will just use the base class which implements approaches that should work for any SQL database.

At the time of writing, the only database-specific subclass is for Postgre SQL. Let’s expand the original table a bit: “name” has now been split into “first_name” and “last_name”.

Let us start with a simple table: UPDATE staff SET salary = 1200 WHERE name = ' Bob'; UPDATE staff SET salary = 1200 WHERE name = ' Jane'; UPDATE staff SET salary = 1200 WHERE name = ' Frank'; UPDATE staff SET salary = 1200 WHERE name = ' Susan'; UPDATE staff SET salary = 1200 WHERE name = ' John'; UPDATE staff SET salary = 1200 WHERE name = ' Bob'; UPDATE staff SET salary = 1250 WHERE name = ' Jane'; UPDATE staff SET salary = 1200 WHERE name = ' Frank'; UPDATE staff SET salary = 1250 WHERE name = ' Susan'; UPDATE staff SET salary = 1200 WHERE name = ' John'; We are no longer setting all the salary fields to the same value, so we can’t collapse it into a single statement.

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