How to use a while loop in SQL Server?
SQL Server Cursor Example Converted to a While Loop. In order to replace this cursor with a WHILE LOOP, we need to create a temporary table to implement a tally table. For all of you who don’t know what a tally table is, we can define it as a table that contains a pair of columns consisting of a key and its value.
When does the SQL statement exit the loop?
As you can see, in each iteration of the loop, the defined condition is checked, and then, according to the result of the condition, the code flow is determined. If the result of the condition is true, the SQL statement will be executed. Otherwise, the code flow will exit the loop. If any SQL statement exists outside the loop, it will be executed.
How to loop through table rows without cursor?
The idea is to loop trough the table rows ordered by the CursorTestID column and update the RunningTotal column with the sum of the CursorTestID column value and the value of the RunningTotal column of the previous row. But before starting, first we need to generate some test rows with the next script.
Do you need a cursor for a loop in SQL Server?
You have always heard that you should avoid cursors in your T-SQL code as a SQL Server best practice, because cursors are detrimental to performance and sometimes cause issues. But sometimes there is a need to loop through the data one row at a time, so in this tip we will look at a comparison of how to do a loop without using cursor.
How are recordsets used to loop through data?
Recordsets have two important properties when looping through data, EOF (End-Of-File) and BOF (Beginning-Of-File). Recordsets are like tables and when you loop through one, you are literally moving from record to record in sequence.
Is it better to use a while loop or a cursor?
If you use global cursors in your code you are taking the risk of facing errors due to a cursor being closed by some stored procedure nested in your code. Usually cursors have less performance than an equivalent loop using a WHILE loop or CTE. There are also benefits to use a WHILE loop compared to a cursor. While loops are faster than cursors.
When to use iterators in a foreach loop?
Iterators enable you to maintain the simplicity of a foreach loop when you need to use complex code to populate a list sequence. This can be useful when you want to do the following: Modify the list sequence after the first foreach loop iteration. Avoid fully loading a large list before the first iteration of a foreach loop.