How to Prove that using subselect queries in SQL is killing performance of server

Posted by adopilot on Stack Overflow See other posts from Stack Overflow or by adopilot
Published on 2010-12-28T12:28:33Z Indexed on 2010/12/28 12:54 UTC
Read the original article Hit count: 310

Filed under:

sql

|

database-design

|

performance-tuning

|

sql-subselect

One of my jobs it to maintain our database, usually we have troubles with lack of performance while getting reports and working whit that base.
When I start looking at queries which our ERP sending to database I see a lot of totally needlessly subselect queries inside main queries.
As I am not member of developers which is creator of program we using, they do not like much when I criticize they code and job. Let say they do not taking my review as serious statements. So I asking you few questions about subselect in SQL

Does subselect is taking a lot of more time then left outer joins?
Does exists any blog, article or anything where I subselect is recommended not to use ?
How I can prove that if we avoid subselesct in query that query is going to be faster ?

Our database server is MSSQL2005

© Stack Overflow or respective owner

Related posts about sql

SQL SERVER – Concat Strings in SQL Server using T-SQL – SQL in Sixty Seconds #035 – Video

as seen on SQL Authority - Search for 'SQL Authority'
Concatenating string is one of the most common tasks in SQL Server and every developer has to come across it. We have to concat the string when we have to see the display full name of the person by first name and last name. In this video we will see various methods to concatenate the strings. SQL… >>> More
SQL SERVER – Concat Function in SQL Server – SQL Concatenation

as seen on SQL Authority - Search for 'SQL Authority'
Earlier this week, I was delivering Advanced BI training on the subject of “SQL Server 2008 R2″. I had great time delivering the session. During the session, we talked about SQL Server 2010 Denali. Suddenly one of the attendees suggested his displeasure for the product. He said, even though… >>> More
Error with SQL Server Setup 2012 on Windows 2012

as seen on Server Fault - Search for 'Server Fault'
I am trying to install SQL Server on Windows 2012. I was able to finally get the wizard up and running after making some changes on the server, but now it fails no matter what I do with the following error: TITLE: SQL Server Setup failure. SQL Server Setup has encountered the following error: … >>> More
How can I detect which version of SQL (eg SQL 2008 or SQL Azure)

as seen on Stack Overflow - Search for 'Stack Overflow'
I need to detect which version of SQL I am dealing with to perorm various tasks, I need specifically detect if I am on SQL 2008 or SQL Azure. How can I do this with detection code written in SQL? >>> More
Nested SQL Select statement fails on SQL Server 2000, ok on SQL Server 2005

as seen on Stack Overflow - Search for 'Stack Overflow'
Here is the query: INSERT INTO @TempTable SELECT UserID, Name, Address1 = (SELECT TOP 1 [Address] FROM (SELECT TOP 1 [Address] FROM [UserAddress] ua INNER JOIN UserAddressOrder uo ON ua.UserID = uo.UserID WHERE ua.UserID = u.UserID ORDER BY uo.AddressOrder ASC) q ORDER BY AddressOrder… >>> More

Related posts about database-design

(Database Design - products attributes): What is better option for product attribute database design

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, I new in database design. What is better option for product attribute database design for cms?(Please suggest other options also). option 1: 1 table products{ id product_name color price attribute_name1 attribute_value1 attribute_name2 attribute_value2 attribute_name3 attribute_value3 } option… >>> More
Book Review: Pro SQL Server 2008 Relational Database Design and Implementation

as seen on SQL Blog - Search for 'SQL Blog'
Investing in proper database design is a very efficient way to cut maintenance costs. If we expect a system to last, we need to make sure it has a good solid foundation - high quality database design. Surely we can and sometimes do cut corners and save on database design to get things done faster… >>> More
Advice on database design / SQL for retrieving data with chronological order

as seen on Stack Overflow - Search for 'Stack Overflow'
I am creating a database that will help keep track of which employees have been on a certain training course. I would like to get some guidance on the best way to design the database. Specifically, each employee must attend the training course each year and my database needs to keep a history of… >>> More
Fiscal year handling strategies in database design

as seen on Stack Overflow - Search for 'Stack Overflow'
By fiscal year I mean all the data in the database (in all tables) that occurred in the particular year. Lets say that we are building an application that allows user to choose from different years. What way of implementing this would you prefer, and why: Separate fiscal year data based on multiple… >>> More
Database design for summarized data

as seen on Stack Overflow - Search for 'Stack Overflow'
I have a new table I'm going to add to a bunch of other summarized data, basically to take some of the load off by calculating weekly avgs. My question is whether I would be better off with one model over the other. One model with days of the week as a column with an additional column for price… >>> More