oracle query optimization tool

Oracle performance optimization operation 11: try to match the like clause at the front end. oracle clause Because the like parameter is frequently used, if the like clause can be indexed, the query efficiency will be greatly improved. Example: Select * from city where name like '% S % '; The execution plan of the

Tags: oracle optimized SQL optimization Base Access tableMethods of accessing dataThere are two types of data in the Access table: 1, direct access to table 2, first access to the index, and then back to the table1, direct access to the table of two ways:①, full table scanFull-table scanning refers to when Oracle accesses the data of the target table, it starts s

generated by map and reduce · Hive.merge.mapfiles = True if and Map output file, default to True· Hive.merge.mapredfiles = False if the Reduce output file is merged, the default is False· Hive.merge.size.per.task = 256*1000*1000 the size of the merged file five, in/exists (not) implements the in operation through the left semi join, and one restriction is that the table to the right of the join can only appear in the join bar Part VI, partition clipping by specifying a partition in the crite

Oracle SQL Performance Optimization: 1. select an appropriate Oracle optimizerThere are three optimizer types in Oracle A. Rule (Rule-based) B. Cost (cost-based) C. Choose (selectivity) Set the default optimizer. You can declare the optimizer_mode parameter in the init. ora file, such as rule, cost, choose, all_rows, a

Decrypt the Oracle backup tool-expimp whether it is an O M worker or a database administrator, data backup and restoration is the focus of our daily work, and a reasonable backup policy is formulated, the use of appropriate backup tools is essential for everyone. Today we will introduce Oracle's backup tools exp and imp. ORACLE databases have two backup methods.

I've seen a private message recently. I asked some optimization questions for Oracle SQL, shared an article about SQL optimization, and later shared some more articles about SQL optimization.(1) Select the most efficient table name order (valid only in the rule-based optimizer):The

reprinted from: Http://www.cnblogs.com/rootq/archive/2008/11/17/1334727.html (1) Select the most efficient table name order (valid only in the rule-based optimizer):The Oracle parser processes the table names in the FROM clause in a right-to-left order, and the FROM clause is written in the final table (the underlying table, driving tables) will be processed first, and in the case where the FROM clause contains more than one table, you must select the

your entire site from stopping accordingly. Because these two operations will lock the table, the table is locked, the other operations are not in. Apache will have a lot of child processes or threads. So, it works quite efficiently, and our servers don't want to have too many child processes, threads and database links, which is a huge amount of server resources, especially memory. If you lock your watch for a period of time, say 30 seconds, then for a site with a high volume of traffic, the 3

The most important component of Oracle SQL uptime is the time spent preparing new SQL statements for execution. However, if you understand the intrinsic mechanism of the executable plan, you can control the time that Oracle spends in assessing the connection order of the tables and improve the performance of the query overall. Prepare the SQL statement provided

Here we only talk about hints-based oracle optimization solutions. In fact, Oracle optimizer has two optimization methods based on Rules (Rule-BasedOptimization, RBO for short) cost-based optimization (Cost-BasedOptimization, referred to as CBO) Here we only talk about hints

be directly read from the memory during the next query to reduce Io. there is also a PGA zone, which is related to the session connected to the user and the area used for sorting. Before 8i, no session is allocated a memory for sorting, and after 9i, all user sessions can be shared, so as to avoid the problem that one session's PGA is not enough while another user's PGA is wasted. In general, the database tuning sequence is: disk (the less the number

; 5, B's unique SELECT * FROM Tbl_emp a right join tbl_dept b to A.deptid = b.id where a.deptid is null; 6, AB AllMySQL full join implementation because MySQL does not support full join, here is the workaroundLeft JOIN + Union (can remove duplicate data) + RIGHT JoinImplemented as in the following code7, A's exclusive + B's exclusiveIntroduction to IndexesWhat is an indexThe official MySQL definition of an index is: index is the data structure that helps MySQL to get data effi

the same Column name ambiguity in multiple tables If you do not use an alias, you can go to the dictionary table to check whether the column name is ambiguous. 12. Replace in not exists with exists instead of not in: Oracle uses the hit-and-return method. in multi-Table link queries, if in is used, the full table traversal of the subquery will be performed, sorted, and merged, in this case, you can use external links or not exists instead. 13. Identi

will introduce the indexing principles to facilitate the following understanding of index optimization: Find the rowid through the index, and then access the table through the rowid. However, if the queried column is included in the index, the second operation will not be performed, because the retrieved data is stored in the index, and access to the index alone can fully meet the query requirements. Note:

Tags: des io ar using SP java for on dataVery good SQL statement optimization 34 article1) Select the most efficient table name order (valid only in the rule-based optimizer):The ORACLE parser processes the table names in the FROM clause in a right-to-left order, and the FROM clause is written in the final table (the underlying table driving tables) will be processed first, and in the case where the FROM cl

partitioned tables:1, the size of the table more than 2GB.2, the table contains historical data, new data is added to the new partition.(3). Advantages and disadvantages of table partitioningTable partitioning has the following advantages:1, improve query performance: The query on the partition object can only search their own care, improve the speed of retrieval.2. Enhance usability: If a partition of a t

(1)Select the most efficient table name sequence (valid only in the rule-based Optimizer ):The Oracle parser processes the table names in the from clause in the order from right to left.,The base table driving table written in the from clause will be processed first. When the from clause contains multiple tables, you must select a table with the least number of records as the base table. If more than three tables are connected for

for SQL optimization are emerging, writing your own SQL tools is always the best way to solve the problem:Select executions, disk_reads, buffer_gets,Round (BUFFER_GETS-DISK_READS)/buffer_gets, 2) hit_radio,Round (disk_reads/executions, 2) reads_per_run,SQL _textFrom v $ sqlareaWhere executions> 0And buffer_gets> 0And (BUFFER_GETS-DISK_READS)/buffer_gets Order by 4 DESC; (17) Improve efficiency with indexes:An index is a conceptual part of a table

Logminer is integrated with oracle as a related log analysis tool. We can use this tool to clearly analyze the changes of all things in related logs and archive logs, and can Logminer is integrated with oracle as a related log analysis tool. We can use this

Label:*sql optimization based on ORACLE11GR2 reading notes * Third, cursor in OracleThe cursor in Oracle is a vector of SQL parsing and execution in an Oracle database and is a data structure for C (Oracle is written in C). There are two types of cursor in an Oracle database