oracle pl sql performance tuning tips techniques

) function. Distinct requires a sort operation, while the others need to perform at least two sorting. Typically, SQL statements with union, minus, and intersect can be overridden in other ways. If your database is well-sort_area_size, using union, minus, intersect can also be considered, after all, they are very readable()optimize GROUP By:Increase the efficiency of the group BY statement by filtering out unwanted records before group by. The followi

Operating Environment: AIX + 11g + PLSQL Includes the following content: 1. SQL statement execution process 2. optimizer and execution plan 3. Properly apply Hints 4. Indexes and Application Instances 5. Other optimization technologies and applications1. SQL statement execution process 1.1 SQL statement execution steps 1) analyze the syntax and analyze whether th

With the SPA, you can play specific types of changes depending on the type of change (such as initialization of change, optimizer statistics refresh, and database upgrade)SQL or the entire SQL payload, and then generate a comparison report that helps you evaluate their impact.In the version number prior to Oracle Database 11g, I had to capture all the

With SPA, you can play a specific stream based on various types of changes (such as initialization parameter changes, optimizer statistics refresh, and database upgrades)SQL or the entire SQL load, and then generate a comparison report to help you evaluate their impact. In versions earlier than Oracle Database 11g, I must capture all

For a period of time performance test, put oneself in the performance test process, use the Oracle used in the SQL statement to organize, do a memo;(1) Multiple fields are spliced in some format"||" string concatenation characters;Example: concatenation of "id" and "code" with commas: select T.id| | ', ' | | T.code fro

))/1000000,2) as Cpu_time,round ((N.CPU_TIME-NVL (o.cpu_time,0))/(( N.EXECUTIONS-NVL (o.executions,0)) *1000000), 2) as Cpu_time_per_exe,round ((N.ELAPSED_TIME-NVL (o.elapsed_time,0))/( (N.EXECUTIONS-NVL (o.executions,0)) *1000000), 2) as Elapsed_time_per_exe "+"From" +newtable+ "n" +"Left JOIN" +oldtable+ "o o.hash_value = n.hash_value and o.address = n.address" +"WHERE n.last_active_time > To_date ('" + sysdate + "', ' yyyy/mm/dd hh24:mi:ss ')" +"and (N.EXECUTIONS-NVL (o.executions,0)) > 0" +"

oracle| Performance | optimization 39. Always use the first column of the index If the index is based on multiple columns, the optimizer chooses to use the index only if its first column (leading column) is referenced by the WHERE clause. Translator by: This is also a simple and important rule. See the following examples. Sql> CREATE TABLE Multiindexusage

statement by filtering out unwanted records before group by. The following two queries return the same result but the second one is obviously much faster. Low efficiency: SELECT JOB, AVG (SAL) From EMP GROUP JOB Having JOB = ' PRESIDENT ' OR JOB = ' MANAGER ' Efficient: SELECT JOB, AVG (SAL) From EMP WHERE JOB = ' PRESIDENT ' OR JOB = ' MANAGER ' GROUP JOB Translator by: This section and section 14 are the same. can skip over. 50. Date of Use When using the date is, be awa

The Oracle tutorial you are looking at is: Oracle SQL Performance Tuning Series learning three. 8. Use the Decode function to reduce processing time Use the Decode function to avoid repeatedly scanning the same record or repeating the same table. For example: SELECT COUNT

Database has always been its own weak item, and now with this article slowly accumulate some of the techniques of Oracle SQL optimization.1. First of all, it is easy to think of all the optimization techniques-index, index What is the use? Indexes do increase query speed when the table data is large, and the index quer

is used, be sure to explicitly delete all temporary tables at the end of the stored procedure, TRUNCATE table first, and then drop table, which avoids longer locking of the system tables.25. Avoid using cursors as much as possible, because cursors are inefficient and should be considered for overwriting if the cursor is manipulating more than 10,000 rows of data.26. Before using a cursor-based method or temporal table method, you should first look for a set-based solution to solve the problem,

involved in the change of the data is a large table, if not used to the index, the efficiency of the query will be affected.NLS_COMP Specifies the collation behavior of the database session.Values: BINARY Normally, comparisons in the WHERE clause and in PL/SQL blocks are binary unless you specify the Nlssort function. Linguistic comparisons for all