advanced oracle sql tuning

the Where condition.Now let's delete the histogram for all the columns in the table.We execute the following SQL so that the owner column is placed in the Where condition.Next we refresh the database monitoring information.We collect statistics on the table using the method_opt = ' For all columns size auto ' method.Then we look at the histogram information.From the above query we can see that Oracle autom

As mentioned in parts 1th and 2nd, there are several relatively easy steps to improve performance you can take, one of these steps involves using an automated tool to "guide" you to write SQL statements, there are many production performance analysis or performance tuning tool manufacturers, in the following article, We will examine one of them. Quest Software Many DBAs and developers use a tool called To

One of the practical skills that can greatly improve the performance of SQL TUNING optimization. When we perform SQL optimization, we often encounter the need to sort a large number of datasets and then retrieve the first part of the results from the sorted set. In this case, when we write SQL statements according to t

SQL Server Performance Tuning 3 Index MaintenancePreface The previous article introduced how to improve database query performance by creating indexes, which is just the beginning. If you do not need proper maintenance in the future, the indexes you have previously created may even become a drag-and-drop attack and a helper for database performance degradation.Search for fragments Removing Fragments may be

Have always wanted to summarize the knowledge of Oracle memory tuning, recently optimized a database memory parameters, look for some information and Google a lot. Now write it down and do the backup. First, overview: Oracle memory can be divided into the system global zone and the process global area in terms of shared and private, that is, the SGA and the PGA

fromV$thread T, V$parameter vWHEREV.name= 'Thread' and(V.value= 0 ORt.thread#=To_number (v.value))) I, (SELECTVALUE fromV$parameterWHERENAME= 'user_dump_dest') D;3.2 Using the Tkprof command to beautify the generated trace fileHere is what I often use, for more detailed instructions on the tkprof command, you can see the tkprof command directly enter.Tkprof xxx.trc xxx.txt Explain=system/Oracle sys=nReference URL: http://www.eygle

(m.shared_memory_committed_kb) as Sharedmemroycommittedkb,sum (M.shared_memory_ RESERVED_KB) as Sharedmemroyreservedkb,sum (m.multi_pages_kb) as Multipageskb,sum (m.single_pages_kb) as SinglePagesKB , SUM (m.multi_pages_kb) +sum (m.single_pages_kb) as Totalpageskbfrom sys.dm_os_memory_clerks MGROUP by M.typeORDER by TOTALPAGESKB DESCYou have sorted by memory usage to find the part that uses the most memory. Analyze the reason for use and resolve.CaseA customer's customer system is used slowly,

large print segments18.count (*) is slightly faster than count (1), of course, if you can retrieve by index, the count of indexed columns is still the fastest. 19. Replace the HAVING clause with a WHERE clause to avoid having a HAVING clause, having The result set is filtered only after all records have been retrieved19. Avoid using like ' * ' to avoid using is null or20.Note:A, programmers pay attention to the amount of data in each table.B, the coding process and the unit test process as far

Tags: des style blog http color using strong AR dataBackgroundMySQL and Oracle were used before, and there was not much use for SQL Server. Recently, due to project reasons, to read the database of other projects, take out a gate of the switch history, and the other side of the use of SQL Server, so the study of SQL Se

Oracle (4) --> advanced subquery (it is difficult to explain multiple examples, but I really don't believe it ~), Oracle Introduction This section will discuss the more complex application of instant queries, mainly to simplify SQL and improve performance from the aspect, of course .. There are many ways to improve per

"Performance Tuning" Oracle AWR reporting metrics full resolution What is AWR? ===================================================================================================== AWR (Automatic workload Repository) A bunch of historical energy data, placed on the Sysaux table space, AWR and Sysaux are all 10g, are the key features of Oracle

be sorted, or it can be added to a column (like joins or additions). Any non-indexed item in the ORDER BY statement, or a computed expression, will slow down the query. Double-check the order BY statement to find non-indexed items or expressions that degrade performance. The solution to this problem is to rewrite the order BY statement to use the index, or you can establish another index for the column you are using, and you should absolutely avoid using an expression in the ORDER BY clause.(a)

articles by Jiang Min's predecessors. Do software developers really know about SQL indexes (clustered indexes) and software development personnel really understand SQL index (index principle), also referred to the song xiaojian predecessors of the article: T-SQL query advanced-detailed description of Public table expr

Run Select Dbms_sqltune.report_tuning_task (: tuning_task) from dual; Error messages, such as the following:Ora-00600:internal error code, arguments: [Kesqsmakebindvalue:obj], [], [],[], [], [], [], []Ora-06512:at "SYS. Prvt_advisor ", line 1624Ora-06512:at "SYS. Dbms_advisor ", line 186Ora-06512:at "SYS. Dbms_sqltune ", line 1008Ora-06512:at Line 8##################Confirmed by MoS, this is a bug. Need to upgrade to 10.2.0.5PSU or 11.2Article:Tuning Advisor terminates with Ora-600[kesqsmakebind

GROUP BY:Increase the efficiency of the group BY statement by filtering out unwanted records before group by. The following two queries return the same result but the second one is significantly faster.Copy CodeThe 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 o

are very readable6. Use where to replace having (if possible)Optimize GROUP BY:Increase the efficiency of the group BY statement by filtering out unwanted records before group by. The following two queries return the same result but the second one is significantly faster. Copy the code code 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 hav

Oracle Advanced query over (partition by...), advanced query .. To facilitate learning and testing, all examples are created under Scott, an Oracle user. create table EMP( empno NUMBER(4) not null, ename VARCHAR2(10), job VARCHAR2(9), mgr NUMBER(4), hiredate DATE, sal NUMBER(7,2), comm NUMBER(7,2), deptno

of data ... God horse is 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 S

In order to be successful, I'll involve some preliminary steps that will be needed to see what happens, including running Plustrce SQL scripts, creating a Explain_plan table, granting roles, configuring Sql*plus environments to view execution plans. All of these steps include "use automatic tracking in Sql*plus" In Oracle