Updating multiple rows without cursor
Let start by creating a simple cursor that will loop through each row in the employee table.
There are 15 rows in the employee table and so this won’t illustrate the performance issues that cursors can suffer but if the table contained The above code creates two variables @Emp Id and @Emp Name that will hold the id and name from the employee table respectively.
I figure I can put the WHILE loop in a UDF and call the UDF in the SELECT clause.
My plan was to raise an error when a circular reference was found but its saying 'Invalid use of 'RAISEERROR' within a function.'.
The dep_id column of employee table will hold values from the id table of the department table, with a one too many relations between the department and employee tables.
Remember this is not a perfectly normalized data table as we just want some data to execute example queries on.
Unfortunately, cursors are extremely slow and so where possible should be replaced with JOINS.
In this article, we will see how cursors process data and look at how and when we can replace cursors with JOINS.Next, we'll declare our cursor, open it and move it to the first record.At the same time we'll read the first film's Oscar wins into the variable we declared earlier. We'll start by setting up the basic structure of the loop and adding a quick test to ensure that our variable is accumulating the number of Oscars.While a cursor is being populated, the table being iterated is locked.Row operations can take a long time to execute depending upon the type of task being performed on each row.
This trigger checks new items for this as they are added and lets us know if they are not. I need a trigger that will recurse up a tree stored in a table looking for circular references.