SQLAuthority News – Learn MySQL Indexing in 99 Minutes – MySQL Indexing for Performance – Video Course

Every year around September 1st, I have decided to do something cool. This is because September 1st is my daughter Shaivi’s birthday. In previous years, I have released my new books as well new courses on this day.  This year I have done something similar for her. I like to work hard and dedicate my efforts to my family as they are the one who provides me unconditional support to do various activities for the community.

Journey to Learn MySQL Indexing in 99 Minutes

Indexes are considered to be sure solution for Performance tuning but it has two sides of the story. A good index can improve performance of your query and bad index can degrade the performance of the query. I have build a course around MySQL indexing where I explain how to create indexes which improves the performances of the MySQL Query by many folds. Indexing is such a subject that I can talk about this subject for many days and still I will have more material to share. However, I had decided to build a course which is very sharp and to the point. I wanted to make sure that with the help of this course one can learn all the major points of MySQL indexes in very short period of the time.

While I was building this course – I had put a threshold that I will not build a very long boring course. I wanted to make sure that I build a crisp course which addresses the need of the hour and teach the most efficient methods to improve performance of the query. It took me more than 3 weeks to build all the material I wanted to cover in this course. Once I have build the material the real challenge was on, I wanted to make sure that I build a course which is basic enough for a novice to understand but advanced enough that an expert can learn various tricks as well. I wanted to balance the course for every level as well as I wanted to make sure that the pace of the course is good enough for everyone to keep up with it.

Finally, after long hours and many days of work, I finalized the content of the course which just is the right fit for everybody – a novice who does not know anything about index as well an expert who already have a clear idea about the index.  I had pretty much mapped out every single minute of the course with the demo and slide. As per my estimate the course should have not gone over 100 minutes. When I was done with the course, I was extremely delighted as the entire course was recorded in 99 minutes – YES, only 99 minutes. I have previously recorded many courses but this course was built with perfection in the seconds of the time.

You can learn MySQL Performance Tuning with the help of Indexing in 99 minutes.

Course Content

Here is the course outline which I have built to learn MySQL Indexing. You can watch this course by creating free trial at Pluralsight. If you do not see the play button to the watch the course, please login to the Pluralsight with your valid credentials.

  • MySQL Indexing for Performance
    • Introduction
  • Types of Indexes
    • Introduction
    • InnoDB vs MyISAM
    • B-Tree Index
    • Advantages of B-Tree Index
    • Clustered Index
    • Advantages of Clustered Index
    • Disadvantages of Clustered Index
    • Secondary Index
    • Building Clustered B-Tree
    • Building Secondary Index B-Tree
    • InnoDB Clustered Table
    • Hash Index
    • Limitation of Hash Index
    • Adaptive Hash Index
    • Building Hash Index
    • Other Indexes
    • Summary in Sixty Seconds
  • Indexing Strategies for High Performance
    • Introduction
    • Effectiveness of Index
    • Demo: List Indexes
    • Demo: Basics of Indexes
    • Demo: Order of Columns in Index
    • Demo: Optimize OR Conditions
    • Demo: Optimize OR Conditions – Advanced
    • Demo: Optimize AND Conditions
    • Demo: Optimize AND Conditions – Advanced
    • Demo: Cover Index
    • Demo: Clustered Index
    • Demo: Index Hints
    • Summary in Sixty Seconds
  • Index Maintenance
    • Introduction
    • MySQL Query Optimizer
    • Statistics
    • InnoDB Statistics
    • Data and Index Fragmentation
    • Index Maintenance
    • Other Index Maintenance Tips
    • Summary in Sixty Seconds
  • Checklists
    • Checklists

Watch Video Course

Click here to watch the MySQL Indexing for Performance video course.

As an author of this course, I have few free codes to watch this course. Please leave a comment to watch this course and I will send a few of the readers a free card to watch this course. You can also request the free code on my Facebook page as I am very active there.

Reference: Pinal Dave (http://blog.sqlauthority.com)

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SQL SERVER – Tips for SQL Query Optimization by Analyzing Query Plan

Update: You can download dbForge Studio for SQL Server for free trial.

One of the most exciting periods of my life relates to the maintenance and optimization of ERP system for one large manufacturing company. The problem was that the system was initially created for a limited range of tasks, which over time grew much bigger than expected.

When multiple users simultaneously used the system, working in it was close to impossible. Increasing the operating capacity of a server could not completely solve the problem. So it was settled on revising current business-functionality and optimizing the most resource-consuming SQL queries.

Before I go on with the article, it’s worth mentioning that SQL Server generates an execution plan for each query. The plan describes an algorithm that will lead to a desired result.

We should also keep in mind how execution plans are generated. To reach maximal query execution speed, query optimizer (separate component of the SQL Server core) always attempts to generate a plan with the sequence of actions that consumes minimum server resources.

When evaluating any execution plan, the query optimizer takes into account multiple factors: involved database objects, conditions of joining them, returned columns list, indexes presence, availability of indexes and actual statistics, etc.

However, sometimes the optimizer cannot operate with the actual data and that is why it can over- or underestimate the SQL query cost when executing different plans. That’s why there is always a chance that the non – optimal plan will be chosen.

SSMS environment allows viewing the execution plan with the help of Show Execution Plan. However, analyzing complicated queries in it is far from easy. That is why I use a more functional query profile available in dbForge Studio for SQL Server.

We can get an execution plan each time SQL query execution is started. To do so, we need to switch to the profiling mode.

Or we can use the Generate Execution Plan command without running the query.

Several examples will let me demonstrate some tips for optimizing SQL queries using the profiler:

1. Minimizing the number of implicit connections

For the most complicated SQL queries I seek to use views depending on the situation, since their declaration might be abundant, and the server will be consuming more time for reading and analyzing this data. I do not intend to say that they should not be used at all, but they should be used wisely.

For example, we should get a list of customer’s tables. All the necessary object data can be obtained from the system views.

SELECT *
FROM sys.tables t

We will get the following plan for this query:

In the profiles the most resource-consuming operation are highlighted with red and yellow accordingly, representing the percentage of resources spent on each operation.

Let's modify our SQL query - now we shall select only table names:

SELECT t.name
FROM sys.tables t

Now our execution plan got simplified and it is obvious that the query execution will require less resources:

How did we achieve that? Let's take a look at the content of sys.tables. Unfortunately, SSMS does not allow viewing system views DLL, so we will use a small trick:

DECLARE @SQL VARCHAR(MAX)
SELECT @SQL = OBJECT_DEFINITION(OBJECT_ID('sys.tables'))
PRINT @SQL

We receive the following results:

CREATE VIEW sys.tables
AS
SELECT
o.name, o.OBJECT_ID, o.principal_id, o.schema_id, o.parent_object_id,
o.TYPE, o.type_desc, o.create_date, o.modify_date,
o.is_ms_shipped, o.is_published, o.is_schema_published,
ISNULL(ds.indepid, 0) AS lob_data_space_id,
rfs.indepid AS filestream_data_space_id,
...
ts.name
AS lock_escalation_desc,
o.is_filetable
FROM sys.objects$ o
LEFT JOIN sys.sysidxstats lob ON lob.id = o.OBJECT_ID AND lob.indid <= 1
LEFT JOIN sys.syssingleobjrefs ds ON ds.depid = o.OBJECT_ID AND ...
LEFT JOIN sys.syssingleobjrefs rfs ON rfs.depid = o.OBJECT_ID AND ...
LEFT JOIN sys.syspalvalues ts ON ts.class = 'LEOP' AND ...
WHERE o.TYPE = 'U'

Query optimizer looks at the columns which are actually used in our SQL query and removes excess joins. Now you can see why the application of an asterisk in query can result in reducing query efficiency.

However the same data can be received in a more efficient way. All tables are objects and are contained in sys.objects:

DECLARE @SQL VARCHAR(MAX)
SELECT @SQL = OBJECT_DEFINITION(OBJECT_ID('sys.objects))
PRINT @SQL
'

We receive the following in Output:

CREATE VIEW sys.objects AS
SELECT
name,
OBJECT_ID,
principal_id,
schema_id,
...
FROM sys.objects$

It's obvious that this view is very simple and thus faster than sys.tables. All we have to do is select the tables among all objects by adding filtering condition (U – USER_TABLE, V - VIEW):

SELECT t.name
FROM sys.objects t
WHERE t.[type] = 'U'

To compare the queries we need to select execution plans and click Compare Selected Results on the context menu.

2. Elimination of data re-reading

Usually data re-reading is one of the most resource-demanding operations. That is why queries should be written in a way that would allow reading data in a query only once.
For example:

SELECT
(
SELECT COUNT(*)
FROM sys.objects o
WHERE o.[type] = 'U')
,(
SELECT COUNT(*)
FROM sys.objects o
WHERE o.[type] = 'V')

When you look through the plan, you can notice that the data from the table is being read twice:

The example below shows how this problem can be resolved:

;WITH cte AS
(
SELECT o.[type], [count] = COUNT(*)
FROM sys.objects o
WHERE o.[type] IN ('U', 'V')
GROUP BY o.[type]
)
SELECT (
SELECT [count]
FROM cte
WHERE [type] = 'U'
)
, (
SELECT [count]
FROM cte
WHERE [type] = 'V'
)

Keep in mind that CTE is just a code generalization - it will not allow you to eliminate the data re-read:

Let's try to rewrite the SQL query using aggregation:

SELECT
COUNT(CASE WHEN o.[type] = 'U' THEN 1 END)
,
COUNT(CASE WHEN o.[type] = 'V' THEN 1 END)
FROM sys.objects o
WHERE o.[type] IN ('U', 'V')

The progress is evident:

But let's imagine that we need to make more than two aggregations. In this case query execution will consume more time. But in fact, we can simplify it even more:

SELECT *
FROM (
SELECT o.OBJECT_ID, o.[type]
FROM sys.objects o
WHERE o.[type] IN ('U', 'V')
)
t
PIVOT
(
COUNT(t.OBJECT_ID) FOR [type] IN (U, V)
)
p

Let's compare the queries:

I suppose, no comments are needed.

To sum it up I would like to point out that simplifying SQL query logic is the key to query optimization.
When analyzing execution plans with the help of the query profiler, you will be able to detect bottlenecks in the performance of databases and improve the efficiency of your SQL queries.

I suggest you download dbForge Studio for SQL Server and try this out. Let me know what you think about the same.

Reference: Pinal Dave (http://blog.sqlauthority.com)

SQL SERVER – Example of Performance Tuning for Advanced Users with DB Optimizer

Performance tuning is such a subject that everyone wants to master it. In beginning everybody is at a novice level and spend lots of time learning how to master the art of performance tuning. However, as we progress further the tuning of the system keeps on getting very difficult. I have understood in my early career there should be no need of ego in the technology field. There are always better solutions and better ideas out there and we should not resist them. Instead of resisting the change and new wave I personally adopt it.

Here is a similar example, as I personally progress to the master level of performance tuning, I face that it is getting harder to come up with optimal solutions. In such scenarios I rely on various tools to teach me how I can do things better. Once I learn about tools, I am often able to come up with better solutions when I face the similar situation next time.

A few days ago I had received a query where the user wanted to tune it further to get the maximum out of the performance. I have re-written the similar query with the help of AdventureWorks sample database.

SELECT *
FROM HumanResources.Employee e
INNER JOIN HumanResources.EmployeeDepartmentHistory edh ON e.BusinessEntityID = edh.BusinessEntityID
INNER JOIN HumanResources.Shift s ON edh.ShiftID = s.ShiftID;

User had similar query to above query was used in very critical report and wanted to get best out of the query. When I looked at the query - here were my initial thoughts

  • Use only column in the select statements as much as you want in the application
  • Let us look at the query pattern and data workload and find out the optimal index for it

Before I give further solutions I was told by the user that they need all the columns from all the tables and creating index was not allowed in their system. He can only re-write queries or use hints to further tune this query.

Now I was in the constraint box - I believe * was not a great idea but if they wanted all the columns, I believe we can't do much besides using *. Additionally, if I cannot create a further index, I must come up with some creative way to write this query. I personally do not like to use hints in my application but there are cases when hints work out magically and gives optimal solutions.

Finally, I decided to use Embarcadero's DB Optimizer. It is a fantastic tool and very helpful when it is about performance tuning.

I have previously explained how it works over here.

First open DBOptimizer and open Tuning Job from File >> New >> Tuning Job.

Once you open DBOptimizer Tuning Job follow the various steps indicates in the following diagram.

Essentially we will take our original script and will paste that into Step 1: New SQL Text and right after that we will enable Step 2 for Generating Various cases, Step 3 for Detailed Analysis and Step 4 for Executing each generated case. Finally we will click on Analysis in Step 5 which will generate the report detailed analysis in the result pan.

The detailed pan looks like. It generates various cases of T-SQL based on the original query. It applies various hints and available hints to the query and generate various execution plans of the query and displays them in the resultant. You can clearly notice that original query had a cost of 0.0841 and logical reads about 607 pages. Whereas various options which are just following it has different execution cost as well logical read. There are few cases where we have higher logical read and there are few cases where as we have very low logical read.

If we pay attention the very next row to original query have Merge_Join_Query in description and have lowest execution cost value of 0.044 and have lowest Logical Reads of 29. This row contains the query which is the most optimal re-write of the original query. Let us double click over it.

Here is the query:

SELECT *
FROM HumanResources.Employee e
INNER JOIN HumanResources.EmployeeDepartmentHistory edh ON e.BusinessEntityID = edh.BusinessEntityID
INNER JOIN HumanResources.Shift s ON edh.ShiftID = s.ShiftID
OPTION (MERGE JOIN)

If you notice above query have additional hint of Merge Join. With the help of this Merge Join query hint this query is now performing much better than before.

The entire process takes less than 60 seconds.

Please note that it the join hint Merge Join was optimal for this query but it is not necessary that the same hint will be helpful in all the queries. Additionally, if the workload or data pattern changes the query hint of merge join may be no more optimal join. In that case, we will have to redo the entire exercise once again. This is the reason I do not like to use hints in my queries and I discourage all of my users to use the same.

However, if you look at this example, this is a great case where hints are optimizing the performance of the query. It is humanly not possible to test out various query hints and index options with the query to figure out which is the most optimal solution. Sometimes, we need to depend on the efficiency tools like DB Optimizer to guide us the way and select the best option from the suggestion provided.

Let me know what you think of this article as well your experience with DB Optimizer. Please leave a comment.

Click to Download Scripts

Reference: Pinal Dave (http://blog.sqlauthority.com)

SQL SERVER – TechEd India 2013 Sessions and Relevent Pluralsight Courses

I am presenting at TechEd India 2013 two SQL Server session. You can read about my session in this blog post.

Yesterday I presented on topic SQL Server Performance Troubleshooting: Ancient Problems and Modern Solutions. Today I will be presenting on the subject Indexes – The Unsung Hero. If you are at TechEd India you must show up in my session – we will have fun talking about Indexes and performance tuning together. You can read about various details about the session over here.

However, if you are not at TechEd India 2013 and still want to know what I am going to cover in the session here is something you can do it. You can watch the following two of my Pluralsight courses which absolutely covers what I am going to talk about in TechEd India 2013.

SQL Server Performance: Introduction to Query Tuning 

SQL Server performance tuning is an art to master – for developers and DBAs alike. This course takes a systematic approach to planning, analyzing, debugging and troubleshooting common query-related performance problems. This includes an introduction to understanding execution plans inside SQL Server.

In this almost four hour course we cover following important concepts.

  • Introduction 10:22
  • Execution Plan Basics 45:59
  • Essential Indexing Techniques 20:19
  • Query Design for Performance 50:16
  • Performance Tuning Tools 01:15:14
  • Tips and Tricks 25:53
  • Checklist: Performance Tuning 07:13

The duration of each module is mentioned besides the name of the module.

SQL Server Performance: Indexing Basics

This course teaches you how to master the art of performance tuning SQL Server by better understanding indexes.

In this almost two hour course we cover following important concepts.

  • Introduction 02:03
  • Fundamentals of Indexing 22:21
  • Practical Indexing Implementation Techniques 37:25
  • Index Maintenance 16:33
  • Introduction to ColumnstoreIndex 08:06
  • Indexing Practical Performance Tips and Tricks 24:56
  • Checklist : Index and Performance 07:29

The duration of each module is mentioned besides the name of the module. You will have to login to watch above courses. 

So if you are going to miss my session at TechEd India, you still have a chance to catch up on what I am going to present by watching the Pluralsight courses listed above.

Reference: Pinal Dave (http://blog.sqlauthority.com)

SQLAuthority News – Presenting Two Technology Sessions at TechEd India 2013 – Today and Tomorrow

Every year I am looking forward to TechEd India as it presents a wonderful opportunity to meet community in first hand. Community is my passion and I love to get involved with it at every single opportunity it presents. This year once again I am presenting a technology session at TechEd India. I will be presenting on the following subject.

Here is something I promise – if you attend my session – when you walk out of my session you will immediate action items which you can use it for your production server and improve the performance of the database. Additionally, I will have some goodies with me for everyone. I will have few of my books, free subscription access to Pluralsight’s library as well something totally interesting as a giveaway.

Here are the details of the sessions:

SQL Server Performance Troubleshooting: Ancient Problems and Modern Solutions

Date: March 18, 2013 – Bangalore
Date: March 25, 2013 - Pune
Time: 2:45 – 3:45 PM

Many believe Performance Tuning and Troubleshooting is an art which has been lost in time. The truth is that art has evolved with the time and there are more tools and techniques to overcome ancient troublesome scenarios. There three major resource when bottlenecked creates performance problem: CPU, IO, and Memory. In this session we will focus on High CPU scenarios detection and their resolutions. If time permits we will cover other performance related tips and tricks. At the end of the session attendee will have clear ideas and action items regarding what to do in when facing any of the above resource intensive scenarios.

Indexes – The Unsung Hero

Date: March 19, 2013 – Bangalore
Date: March 26, 2013 – Pune
Time: 2:45 – 3:45 PM

Slow Running Queries  are the most common problem that developers face while working with SQL Server. While it is easy to blame the SQL Server for unsatisfactory performance, however the issue often persists with the way queries have been written, and how Indexes has been set up. The session will focus on the ways of identifying problems that slow down SQL Server, and Indexing tricks to fix them. Developers will walk out with scripts and knowledge that can be applied to their servers, immediately post the session.

Looking forward to see you in session!

Pluralsight will be sponsoring the TechEd India event and don’t forget to stop by the Pluralsight booth for some goodies and meet the Pluralsight executives.

Reference: Pinal Dave (http://blog.sqlauthority.com)

SQL SERVER – Avoid Using Function in WHERE Clause – Scan to Seek

“Don’t use functions in the WHERE clause, they reduce performance.”

I hear this quite often. This is true but this subject is hard to understand in a single statement. Let us see what it means and how to use the function in the WHERE clause.

We will be using sample database AdventureWorks in this example. Additionally, turn on STATISTICS IO ON settings so we can see various statistics as well.

USE AdventureWorks2012
GO
SET STATISTICS IO ON
GO

Let us first execute following query and check the execution plan and statistics.

-- SCAN - Select values from SalesOrderDetail
SELECT [SalesOrderID], [SalesOrderDetailID], [ModifiedDate]
FROM [Sales].[SalesOrderDetail]
WHERE DATEDIFF(YEAR,ModifiedDate,GETDATE()) < 0
GO

Table 'SalesOrderDetail'. Scan count 1, logical reads 1246

You can see that the above query is scanning the whole table as well even though it is not returning any result it is reading 1246 pages from database.

In this case we are retrieving the data based on the ModifiedDate so we will create an index on the ModifiedDate Column.

-- Create Index on ModifiedDate
CREATE NONCLUSTERED INDEX [IX_SalesOrderDetail_ModifiedDate]
ON [Sales].[SalesOrderDetail] ([ModifiedDate])
GO

Now we have created an index on the ModifiedDate column we will once again execute the same query which we had run earlier.

-- SCAN - Select values from SalesOrderDetail
SELECT [SalesOrderID], [SalesOrderDetailID], [ModifiedDate]
FROM [Sales].[SalesOrderDetail]
WHERE DATEDIFF(YEAR,ModifiedDate,GETDATE()) < 0
GO

Table 'SalesOrderDetail'. Scan count 1, logical reads 338

You can see that the above query is still scanning the whole table as well even though it is not returning any result it is read over 338 pages from database.

The reason for the same is because in the query we are using the function DATEDIFF over the column ModifiedDate. As the outcome of this function is evaluated at the run time, the SQL Server Query engine has to scan the whole table to get necessary data.

To avoid this situation, let us try to avoid using the function on the column of the table and re-write the query. To re-write the query let us first understand what the query is retrieved. It is retrieving all the rows where the year difference between ModifiedDate and Current Date is less than 0. In other words what it means is that we need to retrieve the records which have a future date. We can simply re-write above query in the following way.

-- SEEK - Select values from SalesOrderDetail
SELECT [SalesOrderID], [SalesOrderDetailID], [ModifiedDate]
FROM [Sales].[SalesOrderDetail]
WHERE ModifiedDate > GETDATE()
GO

Table 'SalesOrderDetail'. Scan count 1, logical reads 3

Now let us execute the query and see the execution plan. We can see that there are only 3 logical read now and execution plan is also displaying Seek. This is because now we are not using any function over the column used in the WHERE clause.

To clean up you can run following script to drop the newly created index.

-- Cleanup
DROP INDEX [IX_SalesOrderDetail_ModifiedDate] ON [Sales].[SalesOrderDetail]
GO

In our case both the queries are returning the same result, a simple re-write can make a lot of difference.

Click to Download Scripts

Reference: Pinal Dave (http://blog.sqlauthority.com)

SQL SERVER – Development Productivity Tool – dbForge Studio for SQL Server

I have talked a little bit about dbForge before, but I would like to do a full product review now. Devart’s dbForge Studio for SQL Server is a fantastic tool for SQL Server development, as soon as I installed it I found so many things to learn.

First off, it will increase SQL coding almost instantly. There is very little to learn, you are not just memorizing codes to “cheat” off of. DbForge Studio provides code completion options and automatic SQL formatting, so that you know your code will work. One of my favorite feature is “snippets,” which stores parts of code that you use over and over to cut down on typing and searching – because you know there always a few commands you use again and again! Another time saver is the hints option, which will show you information about objects, and the navigation tool that allows toggling between items using only the F12 key.

Of course, all these features would simply be interesting trivia if you couldn’t design and alter tables, too. But dbForge Studio has that covered as well. Tables are always the hardest part, but with Table Designer, you can quickly set the properties using the visual table editors, then edit the script and rebuild as needed, previewing changes before going live. It really takes a lot of the stress out of altering tables.

Changing your database and the information stored there can also be a stress-filled event. But with Database Diagram tool, you can also edit and manipulate your database quickly and preview changes.  Scaling, grouping, and printing are no problem with Database Diagram. You can also build virtual connections to help visualize your data.

Of course, coding and modifications can seem simple in comparison to tackling the data within the database, especially when there is a complex structure and multiple dependencies. With Schema Compare, you can synchronize your database, even when they are extremely complex. You will also be alerted if there are problems so you can solve problems early, before they become catastrophes.  Schema Compare takes “snap shots” of your SQL Server database for easy comparisons later, which heads off drift. And if you are thinking that this is too good to be true, Schema Compare also has deployment script that help target different SQL Server editions, so it doesn’t matter what version you use, you can still use this tool.

DbForge Studio also allows automating deployment of the database to the production server. There are multiple tools available to help with this, including T-SQL Debugger, Query Profiler, Query Builder, and Data Import & Export. All of these tools can be scheduled and automated, and use easy “point and click” options rather than tedious coding.

While all this automating sounds great, anyone who has had to create and deal with reports is probably wondering if this can be automated, as well. The answer is yes! The Data Report Designer will compile your data and create a report in any of nine formats, so you have the perfect feedback. You can also schedule automatic report delivery.

And last, but certainly not least, let’s deal with the security features in dbForge Studio . I cannot say enough about how important security is, and how well Devart’s tool deals with this subject. The Security Manager feature allows the user to create visual editors for users, log-ins, and roles, and provides a feature for batch editing of objects. Of course, one of the most difficult tasks in security is fine-tuning the security to each individual user. You probably see where I am heading with this – the Security Manager allows setting up different privileges per schema object.

I hope this quick review has convinced some DBAs (and non DBAs!) to give dbForge Studio for SQL Server a try. I am sure you will not be disappointed. I certainly was not! Check out – dbForge Studio for SQL Server.

Reference: Pinal Dave (http://blog.sqlauthority.com)