Which is better cursor or while loop?
While SQL While loop is quicker than a cursor, reason found that cursor is defined by DECLARE CURSOR. Every emphasis of the loop will be executed inside system memory and consuming required server assets.
What are the best approach to do looping in SQL?
3 Answers. Best performing: don’t loop over a table’s rows. Use set-based operations.
How do you optimize a SQL query performance?
25 tips to Improve SQL Query Performance
- Use EXISTS instead of IN to check existence of data.
- Avoid * in SELECT statement. …
- Choose appropriate Data Type. …
- Avoid nchar and nvarchar if possible since both the data types takes just double memory as char and varchar.
- Avoid NULL in fixed-length field. …
- Avoid Having Clause.
Can we use CTE in while loop?
You can’t. Simply place the CTE declaration with in the loop. Or consider materializing the results in a temporary table or table variable.
What is difference between loop and cursor?
Cursors in sql server allow you to fetch a set of data, loop through each record, and modify the values as necessary; then, you can easily assign these values to variables and perform processing on these values. While loop also same as cursor to fetch set of data and process each row in sql server.
When should we use cursor in SQL Server?
In SQL server, a cursor is used when you need Instead of the T-SQL commands that operate on all the rows in the result set one at a time, we use a cursor when we need to update records in a database table in a singleton fashion, in other words row by row.to fetch one row at a time or row by row.
Can we use loop in SQL?
In SQL Server, there is no FOR LOOP. However, you simulate the FOR LOOP using the WHILE LOOP.
How do I run a SQL query in a for loop?
Running a Query Inside the Loop
- WHILE @Counter <= @MaxOscars.
- SET @NumFilms =
- SELECT COUNT(*)
- FROM tblFilm.
- WHERE FilmOscarWins = @Counter.
- SET @Counter += 1.
How do you do a while loop in SQL?
SQL While loop syntax
The while loop in SQL begins with the WHILE keyword followed by the condition which returns a Boolean value i.e. True or False. The body of the while loop keeps executing unless the condition returns false. The body of a while loop in SQL starts with a BEGIN block and ends with an END block.
How do you optimize a query?
It’s vital you optimize your queries for minimum impact on database performance.
- Define business requirements first. …
- SELECT fields instead of using SELECT * …
- Avoid SELECT DISTINCT. …
- Create joins with INNER JOIN (not WHERE) …
- Use WHERE instead of HAVING to define filters. …
- Use wildcards at the end of a phrase only.
How do you optimize a stored procedure?
Improve stored procedure performance in SQL Server
- Use SET NOCOUNT ON. …
- Use fully qualified procedure name. …
- sp_executesql instead of Execute for dynamic queries. …
- Using IF EXISTS AND SELECT. …
- Avoid naming user stored procedure as sp_procedurename. …
- Use set based queries wherever possible. …
- Keep transaction short and crisp.
Are unions faster than two queries?
Preserving performance through UNION
The UNION operation allows us to merge the results of two queries. Since we know that query #1 and query #3 are each significantly faster than query #2, we would expect that the results of the UNION operation will be fast as well.
Why are loops bad in SQL?
Using loops in SQL often leads to “row by agonizing row” processing, which can often be incredibly inefficient. If the list of values is large, consider creating a temporary table with the IDs and then joining the temporary table to the permanent one.
What is CTE in SQL Server with example?
A Common Table Expression, also called as CTE in short form, is a temporary named result set that you can reference within a SELECT, INSERT, UPDATE, or DELETE statement. The CTE can also be used in a View.