Query analysis

Rajendra Gupta
READPAST in the update statements

Explore the SQL query table hint READPAST

November 14, 2020 by

SQL Server creates an optimized execution plan based on the available inputs such as statistics, indexes. By default, it chooses a cost-optimized execution plan and executes the query. Sometimes, we use SQL queries table hints to override the default mechanism. Developers popularly use WITH (NOLOCK) query hint in a Select statement to avoid blocking issues.

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Esat Erkec
SQL Server Query Tuning: Use the UNION ALL operator instead of to UNION operator

Getting started with SQL Server Query Tuning

April 21, 2020 by

This article will cover some essential techniques for SQL query tuning. Query tuning is a very wide topic to talk about, but some essential techniques never change in order to tune queries in SQL Server. Particularly, it is a difficult issue for those who are a newbie to SQL query tuning or who are thinking about starting it. So, this article will be a good starting point for them. Also, other readers can refresh their knowledge with this article. In the next parts of this article, we will mention these techniques that help to tune queries.

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Ahmad Yaseen

Saving your SQL Execution Plan

November 28, 2018 by

In the previous articles of this series (see the index at bottom), we discussed the characteristics of the SQL Execution Plan from multiple aspects, that include the way the SQL Execution Plan is generated by the SQL Server Query Optimizer internally, what are the different types of plans, how to identify and analyze the different components and operators of the Execution Plans, how to work with the plans using different tools and finally, tuning the performance of simple and complex T-SQL queries using the Execution Plans. In this, the last article of this series, but not the least, we will discuss where the Execution plan is stored and how to save it for future use.

Ahmad Yaseen

Using the SQL Execution Plan for Query Performance Tuning

November 23, 2018 by

In the previous articles of this series (see the index at bottom), we went through many aspects of the SQL Execution Plan, where we discussed how the Execution Plan is generated internally, the different types of plans, the main components and operators and how to read and analyze the plans that are generated using different tools. In this article, we will show how we can use an Execution Plan in tuning the performance of T-SQL queries.

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Ahmad Yaseen

A new SQL Execution Plan viewer

November 20, 2018 by

In the previous articles of this series (see the index at bottom), we discussed many aspects of the SQL Execution Plans, starting with the main concept of SQL Execution Plan generation, diving in the different types of the plans and showing how to analyze the components and operators of the SQL Execution Plans.

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Ahmad Yaseen

SQL Server Execution Plan Operators – Part 4

October 29, 2018 by

In the previous articles of this series, we went through three sets of SQL Server Execution Plan operators that you will meet with while working with the different Execution Plan queries. We described the Table Scan, Clustered Index Scan, Clustered Index Seek, the Non-Clustered Index Seek, RID Lookup, Key Lookup, Sort, Aggregate – Stream Aggregate, Compute Scalar, Concatenation, Assert, Hash Match Join, Hash Match Aggregate , Merge Join and Nested Loops Join Execution Plan operators. In this article, we will dive in the fourth set of these SQL Server Execution Plan operators.

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Ahmad Yaseen

SQL Server Execution Plan Operators – Part 3

October 29, 2018 by

In the previous articles of this series, we discussed a group of SQL Server Execution Plan operators that you will face when studying the SQL Execution Plan of different queries. We showed the Table Scan, Clustered Index Scan, Clustered Index Seek, the Non-Clustered Index Seek, RID Lookup, Key Lookup and Sort Execution Plan operators. In this article, we will discuss the third set of these SQL Execution Plan operators.

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Ahmad Yaseen

SQL Server Execution Plan Operators – Part 2

October 26, 2018 by

In the previous article, we talked about the first set of operators you may encounter when working with SQL Server Execution Plans. We described the Non Clustered Index, Seek Execution Plan operators, Table Scan, Clustered Index Scan, and the Clustered Index Seek. In this article, we will discuss the second set of these SQL Server execution plan operators.

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Ahmad Yaseen

SQL Server Execution Plan Operators – Part 1

September 12, 2018 by

In the previous articles of this series, SQL Server Execution Plans overview , SQL Server Execution Plans types and How to Analyze SQL Execution Plan Graphical Components, we discussed the steps that are performed by the SQL Server Relational Engine to generate the Execution Plan of a submitted query and the steps performed by the SQL Server Storage Engine to retrieve the requested data or perform the requested modification operation.

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James Rhoat

Performance troubleshooting when the query plan from the application is different than SSMS

August 24, 2018 by

Troubleshooting performance issues in a database is one of the main jobs of DBAs and by now most can trace the problem back to a query which is either running to slow or is causing a blocking issue on a key table. However, what is often not known is why this doesn’t cause problems in SSMS or why you don’t get the same query plan as what is inside the app. For example, in your extended event trace you see the query running longer from the application when compared to SSMS.

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Ahmad Yaseen

SQL Server Execution Plans types

July 23, 2018 by

In the previous article, we described, in detail, the different stages that a submitted SQL Server query goes through and how it processed by the SQL Server Relational Engine. The SQL Server Relational Engine generates the Execution Plan and the SQL Server Storage Engine performs the requested data retrieval or modification process. In this article, we will discuss the different types and formats for SQL Server Execution Plans.

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Aamir Syed

Use cases for Query Store in SQL Server

July 18, 2018 by

Query store was introduced in SQL Server 2016. It is often referred to as a “flight data recorder” for SQL Server. Its main function is that it captures the history of executed queries as well as certain statistics and execution plans. Furthermore, the data is persistent, unlike the plan cache in which the information is cleared upon a server restart or reboot. You can customize, within Query Store, how much and how long the query store can hold the data.

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Esat Erkec

Main Concepts of SELECT operators in SQL Server execution plans

July 9, 2018 by

One of the main responsibilities of a database administrator is query tuning and troubleshooting query performance. In this context, SQL Server offers several tools to assist. But among them, query execution plans are essential for query optimization because they include all of the vital information about the query execution process. At the same time as it provides this valuable information “under the hood”, SQL Server creates a graphical description of the execution plan. Read more »

Ahmad Yaseen

SQL Server Execution Plans overview

July 4, 2018 by

In this series of articles, we will navigate the SQL Server Execution Plan ocean, starting from defining the concept of the Execution Plans, walking through the types, components and operators of Execution Plans analyze execution plans and we’ll finish with how to save and administrate the Execution Plans.

When you submit a T-SQL query, you tell the SQL Server Engine what you want, but without specifying how to do it for you. Between submitting the T-SQL query to the SQL Server Database Engine and returning the query result to the end user, the SQL Server Engine will perform four internal query processing operations, to convert the query into a format that can be used by the SQL Server Storage Engine easily use to retrieve the requested data, using the processes assigned to the SQL Engine from the Operating System to work on the submitted query.

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