SQA server performance tuning
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This document discusses SQL Server performance tuning. It covers indexing to improve query performance by creating indexes on frequently searched columns. It also discusses rewriting queries to use appropriate operators like = instead of intrinsic functions, and to rewrite subqueries as joins. SQL Server tools like execution plans and SQL Profiler can analyze queries and identify bottlenecks. The presenter is from ANS-ASIA, a software development company in Vietnam, and has 6 years of experience with SQL Server, .NET and other technologies.
![SQLServer tools to improve performance.
Execution plan
CREATE TABLE Employees
(
Id BIGINT NOT NULL,
Name VARCHAR(20) NOT NULL,
Dept VARCHAR(10),
CONSTRAINT [PK_Employee] PRIMARY KEY
CLUSTERED
(Id ASC)
)
CREATE TABLE Employees_Mid
(
Id BIGINT NOT NULL,
Name VARCHAR(20) NOT NULL,
Dept VARCHAR(10),
CONSTRAINT [PK_Employee_Mid] PRIMARY KEY
CLUSTERED
(Id ASC)
)
Query 01
INSERT INTO Employees(Id, Name, Dept)
SELECT Id, Name, Dept FROM Employees_Mid
WHERE Employees_Mid.Id = 1000
Query 02
INSERT INTO Employees(Id, Name, Dept)
SELECT Id, Name, Dept FROM Employees_Mid
WHERE Employees_Mid.Name = ‘A00001’](https://image.slidesharecdn.com/anssqlserverperformancetuning-final-140403053822-phpapp01/85/SQA-server-performance-tuning-17-320.jpg)
SQA server performance tuning
- 1. SQLSERVER PERFORMANCE TUNING Presenter: Trịnh Hồng Chương
- 2. AGENDA About my company – ANS-ASIA, and me About SQL Performance Indexing Rewrite query SQLServer tools to improve performance.
- 3. ABOUT 100% subsidiary of ANS Japan Address : 10F CMC Tower, Duy Tan Street Foudation : November 2012 Employees : 30 Business function :Business function : Software development Enterprise system (100% Japanese customer up to now) (Sales management system, Enterprise system for transportation industry, Tuition management system for university...) IT consulting
- 4. ABOUT ME Name: Trinh Hong Chuong Skill: 6 years experience in software development (.Net (VB.Net, C#), T-SQL, PL-SQL, VBA) Beginner in PHP, PostgreSQL Interesting in: Reading book, listening music, walking alone, travelling, ….walking alone, travelling, ….
- 5. SQL PERFORMANCE Assess the problem and establish numeric values that categorize acceptable behavior. Measure the performance of the system before modification. Identify the part of the system that is critical for improving the performance. This is called the bottleneck. improving the performance. This is called the bottleneck. Modify that part of the system to remove the bottleneck. Measure the performance of the system after modification. If the modification makes the performance better, adopt it. If the modification makes the performance worse, put it back the way it was.
- 6. WHAT’S INDEXING Index is shortcuts to real data Data type structure: B-Tree Types of indexes: Clustered, Non-Clustered, XML index, Fulltext index
- 7. WHY’S INDEXING An index is used to speed up searching in the database. Indexes can be helpful for a variety of queries that contain SELECT, UPDATE, DELETE, or MERGE statements. Less items in primary keyLess items in primary key
- 8. CLUSTERED INDEX Clustered indexes sort and store the data rows in the table or view based on their key values. root Id(from 1 to 4) Id(from 5 to 7)Id(from 1 to 4) Id(from 5 to 7) Id 1 Name Bill Dept Dev Id 2 Name Jobs Dept HR Id 7 Name Gate Dept R&D
- 9. NON-CLUSTERED INDEX A nonclustered index contains the nonclustered index key values and each key value entry has a pointer to the data row that contains the key value. root Name(from A to F) Name Bill Id 1 Name Gate Id 7 Name Jobs Id 2 Name(from G to M) Name(from N to Z)
- 10. IMPROVE INDEX Create Highly-Selective Indexes Indexing on columns used in the WHERE clause of your critical queries frequently improves performance. Selectivity is the ratio of qualifying rows to total rows. If the ratio is low, the index is highly selective. Create Multiple-Column IndexesCreate Multiple-Column Indexes
- 11. REWRITE QUERY Use a search argument (SARG) SARG operators include =, >, <, >=, <=, IN, BETWEEN, and sometimes LIKE (in cases of prefix matching, such as LIKE ‘Bill%') Non-SARG operators include NOT, <>, NOT EXISTS, NOT IN, NOT LIKE, and intrinsic functions
- 12. REWRITE QUERY Rewrite sub-query into JOIN Bad sample Good sample SELECT "Order ID" SELECT DISTINCT O."Order ID" FROM Orders O WHERE EXISTS (SELECT "Order ID" FROM "Order Details" OD WHERE O."Order ID" = OD."Order ID" AND Discount >= 0.25) FROM Orders O INNER JOIN "Order Details" OD ON O."Order ID" = OD."Order ID" WHERE Discount >= 0.25
- 13. REWRITE QUERY Don’t use intrinsic functions, type conversion on index column Bad sample Good sample DECLARE @limitId = 10 SELECT Name FROM Employees DECLARE @limitId = 10 SELECT Name FROM EmployeesEmployees WHERE Id - 1 = @limitId Employees WHERE Id = @limitId + 1
- 14. REWRITE QUERY Use parameterizied queries Query only you must About Performance, cursor less than base-query
- 15. REWRITE QUERY Index the ORDER-BY / GROUP-BY CREATE INDEX Emp_Name ON Employees ("Last Name" ASC, "First Name" ASC) Can help optimize Will not help optimize ... ORDER BY / GROUP BY "Last Name" ... ... ORDER BY / GROUP BY "First Name" ...Name" ... ... ORDER BY / GROUP BY "Last Name", "First Name" ... "First Name" ... ... ORDER BY / GROUP BY "First Name", "Last Name" ...
- 16. REWRITE QUERY Index the DISTINCT CREATE INDEX Emp_Name ON Employees ("Last Name" ASC, "First Name" ASC) Can help optimize Will not help optimize ... DISTINCT "Last Name", "First Name" ... ... DISTINCT "First Name" ... ... DISTINCT "Last Name" ...Name" ... ... DISTINCT "First Name", "Last Name" ... ... DISTINCT "Last Name" ...
- 17. SQLServer tools to improve performance. Execution plan CREATE TABLE Employees ( Id BIGINT NOT NULL, Name VARCHAR(20) NOT NULL, Dept VARCHAR(10), CONSTRAINT [PK_Employee] PRIMARY KEY CLUSTERED (Id ASC) ) CREATE TABLE Employees_Mid ( Id BIGINT NOT NULL, Name VARCHAR(20) NOT NULL, Dept VARCHAR(10), CONSTRAINT [PK_Employee_Mid] PRIMARY KEY CLUSTERED (Id ASC) ) Query 01 INSERT INTO Employees(Id, Name, Dept) SELECT Id, Name, Dept FROM Employees_Mid WHERE Employees_Mid.Id = 1000 Query 02 INSERT INTO Employees(Id, Name, Dept) SELECT Id, Name, Dept FROM Employees_Mid WHERE Employees_Mid.Name = ‘A00001’
- 18. EXECUTION PLAN – QUERY 01
- 19. EXECUTION PLAN – QUERY 02
- 20. SQLServer tools to improve performance. SQL Profiler