how to tune sql query in oracle

Here we will introduce more than 40 useful Oracle query statements, covering date operations, server information retrieval, execution status retrieval, database size calculation, and other queries. These are essential skills for all Oracle developers. Address: http://www.jbxue.com/db/19890.html Date/time query 1. Obtai

Oracle connection query and oracle connection I have learned inner join and outer join in SQL Server. outer join is divided into left outer join andRight outer join ). In Oracle, the external connection between two or more tables is represented by (+. Code Demo: Check the na

condition in Statement 7 after the on clause.Select o. id, o. order_number, o. customer_id, c. id, c. nameFrom orders o left outer join MERs c on c. id = o. customer_id and o. order_number The query results of statement 7 and statement 8 are obviously different, and the results displayed in Statement 8 are hard to understand. Therefore, when writing a join query, we recommend that you only follow the join

Transferred from: http://www.oracle.com/technetwork/cn/articles/hartley-recursive-086819-zhs.htmlRecursive database processing, also known as BOM or part decomposition , applies to a wide range of applications, including human resources, manufacturing, financial markets and education. The data involved in such processing is called tree structure data or hierarchical data. Oracle databases have long supported recursion through specialized syntax (CONN

Oracle multi-Table query, oracle Basic multi-Table query syntax The implementation of cartesian products in SQL is not only Cross Join ). All join methods are converted into temporary Cartesian Product tables. Cartesian product is a concept in relational algebra, which indi

Simple oracle query, simple oracle Data Query uses the SELECT command to extract information from the database table. Syntax structure: simple query SELECT * | column name | expression FROM table name WHERE condition order by column name Syntax Parsing:* Indicates all co

1. SQL statements Is a language Meets ANSI standards Keyword cannot be abbreviated Use statements to control the definition information and data of tables in the database SQL is the abbreviation of Structured Query Language (Structured Query Language. You can use SQL statem

visits to the database: Oracle has performed a lot of work internally: parsing SQL statements, estimating the index utilization, binding variables, and reading data blocks; (5) re-set the arraysize parameter in SQL * Plus, SQL * forms, and Pro * C to increase the retrieval data volume for each database access. The rec

This article describes the concepts and operations of Partitioned Tables from the following aspects:1. Concepts of tablespaces and partition tables2. Specific functions of table partitions3. Advantages and Disadvantages of table partitions4. Table partition types and operation methods5. maintenance operations on table partitions.(1) concepts of tablespaces and partition tablesTablespace:Is a collection of one or more data files. All data objects are stored in the specified tablespace, but they a

possible execution plans and determines the quality or cost of each plan in order to obtain information about the current database state and finally select the best execution plan. Because the query optimizer may be imperfect, database users and administrators sometimes need to manually check and tune the optimizer-generated plans for better performance. Now you know what a good execution plan is.As p

Tags: Oracle SQL performance optimizationConcept: Sub-query unwrapping (subquery unnesting) is an optimization of the target SQL that the optimizer handles for the band query, which means that the optimizer no longer treats the target SQ