The strategy selected by the query optimiser to process a query.

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A query executed in a backup of a database is performing better than if executed in the original database

We have two databases with the same data, let's call it Database A which is the original and Database B which is the backup from Database A. A query is performing much better in Database B for example ...
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2answers
163 views

Execution Plans Query

I want to check the estimated number of rows of a query in MS SQL Server. I can right click on the query and select "display estimated execution plan". but I want to do the exact thing with a hard ...
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66 views

Reading a SQL Server Execution plan

I am very new to any type of tuning but have been learning more.. One of my specific databases one of the problems identified with slow queries are a number of Implicit conversions. It is my ...
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80 views

Different Execution Plans Picked for Similar Queries

Thank you in advance for reading it. This question is kind of long and need a little patience to read. I will provide as much details as I can to void interference factors to solve this problem. ...
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1answer
79 views

Print the execution time on messages Pane?

How I can print the execution time of each query on messages Pane? For example the Select * from tbl1 runs for 10 mins then Select * from tbl2 runs for 15mins and so on.. Select * from tbl1 Go Select ...
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76 views

What to look for in query execution plans? [closed]

Assuming the query execution is slow, I have collected the xml plan. What should I look for in the actual execution plan. What are the top 10 things I need to watch out for? I know this is a broad ...
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81 views

How many LEFT JOINS make a VIEW unusable?

I have a view which involves LEFT JOINS on 20+ tables to a base table but when querying this view and looking at the execution plans I am getting something totally unexpected. For example, with the ...
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1answer
108 views

Oracle 10g: same query, different plans on copies of the same DB

I have a query joining a number of long tables (primary key in one table, indexed column in another) which results in different plans on different copies of the same database. The structure of copies ...
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48 views

Access and filter in oracle plan

I came to a execution plan where oracle choose to access the index but instead of using the columns as predicate it only filter by them. My question is what are the reasons that can cause that(all ...
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63 views

Comparing execution plans [closed]

How does the optimizer compare different execution plans of the same query? Let's say we have two complex and structurally different execution plans, how can I know if they are providing the same ...
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1answer
2k 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. ...
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121 views

SQL Server Index Scan Actual Executions

I have a fairly complicated query and running it on two databases with same schemas, but with different data produces different result. On database D1 the elapsed time is around 1 second, and the ...
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482 views

Query performance and join hints, plan cost, and duration

Having some trouble identifying why a query's duration would decrease when using OPTION (HASH JOIN) or OPTION (MERGE JOIN), although plan cost increases. Background I have a reporting database using ...
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59 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, ...
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58 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 ...
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24 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?
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120 views

Explain difference between insert as select and select

Can someone explain why there is plan difference? Same query, same time the explain plan taken. I understand what happen (different order of getting the data) and how to fix it(move to forall insert ...