0
votes
0answers
53 views

Index Tuning Question

I have the following query: SELECT T1.ITEMID, T1.ITEMTYPE, T1.PURCHMODEL, T1.HEIGHT, T1.WIDTH, T1.SALESMODEL, T1.COSTGROUPID, T1.REQGROUPID, T1.EPCMANAGER, ...
5
votes
2answers
337 views

Index seek much slower with OR condition compared with separate SELECTs

Based on these questions and the answers given: SQL 2008 Server - performance loss possibly connected with a very large table Large table with historical data allocates too much of SQL Server 2008 ...
0
votes
0answers
45 views

same query different servers,different execution plan and time

I have this query and it runs less than 2 minutes on Test but on Prod it takes 10 minutes. Both are the same version,CPU,RAM,OS the same. I have four tempdb files on Prod but one one Test. I ...
1
vote
1answer
142 views

Understanding execution plans using TVPs

I have some slow running queries (8 seconds across 1M records grouped by months) and have been trying to make sense of the execution plans. We use around 10 TVPs to send in a set of filters that the ...
2
votes
1answer
111 views

Is there any difference on performance when choosing DISTINCT or GROUP BY to bring distinct values?

I would like to know if there is any difference concerning performance when choosing DISTINCT or GROUP BY to bring distinct rows from a query. I've tried comparing the execution plans, but they seem ...
2
votes
1answer
76 views

High I/O for part of query

I have a large query that I'm trying to tune. I write lots of queries but haven't done a lot of tuning. I've included a screenshot from SQL Sentry Plan Explorer Free (SSPEF): In the above part of ...
0
votes
0answers
17 views

Analize Query in MySQL Server 5.1

I try use MySQL Workbench 6 to analyze the cost, but they don't show the cost of query. How i get this costs?
4
votes
2answers
527 views

Why is my plan guide not being used?

We recently ran into the tipping point issue and some of our report queries that used to complete execution within a couple of seconds are now taking more than 2 min because the query optimizer simply ...
3
votes
1answer
71 views

Every query plan statistic says my query should be faster, but it is not

I have a bit of a odd situation. I have two queries that produce the same result, according to SSMS and SQL Sentry Plan Explorer the first query should cost 95% and the 2nd query should cost 5%. ...
0
votes
1answer
1k views

Different execution plan for the same query if I change a value in the predicate

I am getting two different execution plans for the same query only by changing the value in the predicate, the first one uses nested loops and the other one hash join which takes a lot longer. ...
3
votes
1answer
191 views

Optimizing complex join predicates [closed]

Table Definitions CREATE TABLE [dbo].[Pin_Mtg] ( [MtgId] bigint NULL, [CntyCd] char(5) NOT NULL, [BatchDt] int NOT NULL, [BatchSeq] int NOT NULL, [MtgSeq] tinyint NOT NULL, ...
4
votes
2answers
118 views

Performance of different precedence pseudocolumn solutions with LIMIT

I was wondering about the relative performance of the solutions provided in the answers to a question on stackoverflow, I decided to run some tests. The OP wanted to get the first matching row given ...
4
votes
2answers
210 views

Performance on SQL Join

I have a query which takes ages to run mainly due to a join between 2 tables on a PK and FK. The Key is prefixed with 2 letters (which is always the same, RN) followed by 7 digits So RN1234567 for ...
12
votes
2answers
2k views

How (and why) does TOP impact an execution plan?

For a moderately complex query I am trying to optimize, I noticed that removing the TOP n clause changes the execution plan. I would have guessed that when a query includes TOP n the database engine ...
15
votes
2answers
1k views

T-SQL query using completely different plan depending on number of rows I'm updating

I have a SQL UPDATE statement with a "TOP (X)" clause, and the row I'm updating values in has about 4 billion rows. When I use "TOP (10)", I get one execution plan that executes almost instantly, but ...
2
votes
1answer
253 views

Query tuning - SQL Server

One of our developers are trying to run the below query on a development server, which involves pulling data from a linked server, production. The query ran for more than 14 hours before it was ...