not as good as Oracle ...!!!There are some children's shoes simply think that SQL Server is pediatrics, there is no technical content ... It's very simple.On these points, I don't want to spit out anything, I just want to let those friends who really know SQL Server to prove something to SQL Server.At the end of the a
filtering out unwanted records before group by. The following two queries return the same result but the second one is significantly faster.The code is as follows:Low efficiency:SELECT JOB, AVG (SAL)From EMP GROUP job has job = ' president ' and AVG (SAL) >xxxEfficient:SELECT JOB, AVG (SAL)From EMPWHERE JOB = ' President 'OR job = ' MANAGER ' GROUP JOB having and AVG (SAL) >xxx7, usually, if the statement can avoid the use of subqueries, as far as possible without sub-query.Because the overhead
Oracle's Optimizer:There are two types of optimizations for Oracle: The rule-based optimizer (Rbo/rule based optimizer) and the cost-based optimizer (Cbo/cost based optimizer).Sometimes, it indicates that there is an index, but the query process obviously does not use the relevant index, causing the query process to take a long time, the resource is huge, where is the problem? First, we want to determine what optimization mode the database is running
In the past decade,OracleIt has become one of the most professional databases in the world. For IT experts, IT is to ensure that their company's productivity is improved by leveraging the powerful features of Oracle. One of the most effective methods isOracle Optimization. It has a lot of parameters and technologies to improve the performance of your Oracle database. The following describes how to optimize
. Create_snapshot;
We can also use the Dbms_workload_repository package to complete the baseline, the default settings and other operations.ADDM (Automatic Database diagnostic Monitor AWR)Oracle is an internal consulting system, can automatically complete the most database of some optimization recommendations, giveSQLThe optimization, the creation of the index, the collection of statistics and other suggestions.ADDM report Generation:Sqlplus>@?/rdbms/
Oracle Database 10g Performance Tuning tips and techniques is recommended. For Oracle performance test, diagnosis, analysis, and optimization, see!
Chapter 2 Basic index principles (beginner developer and beginner dBA). For Oracle index optimization, refer!
Chapter 4 tuning
Tags: tabs Other applications ABS SSE contains increased data process structure understandingThe parameters of the tuning function in the Oracle database system are called initialization parameters, and the database administrator needs to properly adjust these initialization parameters to optimize the Oracle system according to the actual situation.1 introduction
Summary: This article begins with a detailed introduction to the concept of shared pool in Oracle and the memory structure included. It then provides an in-depth overview of Oracle's management mechanisms for shared pool. Finally, the paper introduces the practical method of buffer cache monitoring and tuning.
1. The concept of shared pool
Oracle databases, as
. Careful use of large temporary tables and other large table connection query and modification, reduce the system table burden, because this operation will be in one statement multiple times the system table of tempdb. d) Rational use of the algorithm: based on the SQL optimization techniques mentioned above and the SQL optimization content in the ASE Tuning ma
of disk sorting will be greatly increased. This is mainly because at the end of the month, users will make statistics on the transaction data for the month. So at the beginning of the month, because of the number of transactions, so there will be more disk sorting occurs. In this case, it is necessary for the database administrator to adjust the relevant parameters. However, this adjustment is a temporary adjustment, until the cycle has passed, still need to transfer the parameters back. Only i
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The customer provided an AWR report during peak hours. After careful analysis, it was found that it was a high-CPU-consuming SQL statement, which only took 85% of the CPU, this gives us an in-depth understanding of SQL optimization. We have also done some DB optimization before, basically through analysis tables, index creation, parameter adjustment, PATCH, and so on. However, this time, it lasted for a w
. server.2005. Technical Insider "series
Conclusion This article first to this bar, short, easy to understand, this article mainly introduces the query plan of the joint operators, the next we analyze SQL Server parallel operations, in multicore hyper-threading gathered today, see SQL How server uses parallel operations to maximize the use of existing hardware resources to improve performance, is inte
Tag: Time Condition number column arch OSI user CTE codeIn section 1.5 of the SQL Tuning Basics Overview 05-oracle Index Type and introduction, several "Common index execution plans" are mentioned:
Index full Scan: Fully scanned indexes, block read, orderedIndex range Scan: Range sweep of indexIndex fast full Scan: Fast all scans of indexes, multiple rea
Io is very relevant, when the free buffer waiting in the v$session_wait of the entry is very small or not, Explain the DBWR process of your system will be enough, do not need to adjust, there are many items of free buffer wait, your system must feel very slow, then your DBWR is not enough, the resulting wio has become your database performance bottlenecks, the solution is as follows:
A.1 to increase the write process while adjusting the db_block_lru_latches parameters
Example: Modify or add the
the deterioration of performance is a variety of factors, and sometimes the results of the performance degradation caused by multiple elements, this requires the database administrator has a more comprehensive computer knowledge, can be sensitive to the impact of the database performance of the main reason. In addition, good database management tools are also important for optimizing database performance.
Database performance optimization tools commonly used in
Document directory
Preliminary steps
Using bind variables
There are several relatively easy steps you can take to improve performance. From the user's perspective, one of the most frequently used interfaces with a database involves SQL statements, so getting a handle on them is a good place to start, in terms of being able to see an immediate improvement. -->Oracle
does not exist in the table. (2) ' | | ' is a character join function. As with other functions, the index is deactivated. (3) ' + ' is a mathematical function. As with other mathematical functions, the index is deactivated. (4) The same index columns cannot be compared to each other, which will enable full table scanning.(+)A. If the number of records in a table that has more than 30% data is retrieved. Using indexes will have no significant efficiency gains.B. In certain situations, using an i
The Association of SQL tuning and shared pool structures introduces three types of computer resources that affect performance: Memory, CPU, and I/O. By adjusting SGA and PGA to make full use of physical MEMORY, making full use of CPU through parallel processing, and making full use of Hard Disk processing power by adjusting I/O distribution. Server process and PGA are "two grasshoppers on one rope", so sp a
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