by index

Original address: https://www.cnblogs.com/Dreamer-1/p/6076440.htmlOne: What is the Oracle execution plan?Execution plan is a description of the execution process or access path of a query statement in OracleTwo: How to view Oracle execution

I. Nested loop principleNested loop connection (loop nested connection) refers to a two-table connection, which is followed by a two-tier nested loop to match sequentially, and finally gets the table join method that returns the result set.If the

Index can improve the performance of the query, if no INDEX,MONGODB must scan the entire collection, starting with the first doc of collection, until the last doc, even if all doc after the first Doc does not meet the query criteria. If there is a

The Dbms_xplan package includes a series of functions, primarily for displaying the execution plan of the SQL statement, and using different functions to display in different situations, such as an estimated execution plan usingThe display function,

You may have heard about the built-in methods of array objects. Today we will mainly introduce the built-in methods of array objects in JavaScript. If you are interested, refer to the following, hope to help you learn javascript /** * This article

[Database] How much performance will oracle index reconstruction improve? During work, we often observe the space release and Application Performance Improvement brought about by index reconstruction. Space release is easy to understand and measure.

I. Basic Concept: Oracle started at 11g and provided a new method for fixed execution plans, namely, SQL plan baseline, Chinese name SQL Execution plan baseline (baseline for short ), it can be considered as an improved version of OUTLINE or SQL

Oracle11g recursion + exists Execution Plan Change There is a recursive query that runs fast on 10g, but cannot run on 11g.SQL> select * from v $ version;BANNER--------------------------------------------------------------------------------Oracle

--- ProblemSelect owner, index_name, DEGREE from DBA_INDEXES where DEGREE> 1*ERROR at line 1:ORA-01722: invalid number.-- 1 get execution trace informationSQL> set autotrace traceonlySQL> select owner, index_name, DEGREE from DBA_INDEXES where

How to create an oracle Function IndexAn important new feature of Oracle8i is the addition of the function-based index (hereinafter referred to as the FBI ).With this feature, Oracle DBA can use functions or expressions in the index. These functions

Rownum is a pseudo column that generates a serialized number based on the returned records. With rownum, we can produce some output results that were originally hard to implement, but because it is a special feature of pseudo columns, we also need

We know that Oracle optimizer is missing in Oracle Database 10 GBThe saving mode is changed from the previous choose to the current all_rows. SQL> show parameter optimizer_mode Name type value----------------------------------------------------------

Oracle table connection and oracle connectionI. nested loop PrincipleA nested loop connection is a two-layer nested loop that matches two tables in sequence and returns the table join method of the returned result set.In the following SQL statement,

Oracle Index Clustering Factor (cluster Factor) I. Description: During the test today, we found that there was an index on the field, but the execution plan did not go through the index. After searching on the internet, we found that it was caused

1.1.1 Summary If we want to optimize the database, we can optimize the database system using the following five methods. 1. Computer hardware optimization2. Application Optimization3. Database INDEX OPTIMIZATION4. SQL statement Optimization5.

Operating System: rhel5.4x86, database: Oracle11gR2. Experiment Description: This experiment aims to show that the B-Tree index performance is better than the BitMap index. Read from consistency Operating System: rhel 5.4x86, database: Oracle 11g R2,

First of all, the following refers to the Oracle database is the most common B-tree index, Oracle data Other types of indexes are not considered, B-tree index is like a long tree, it contains two types of data blocks, one is the index branch block,

The autotrace switch is opened in the Sqlplus can also get the target SQL execution plan, but also can get the target SQL at the execution of the resource consumption, that is, by setting the autotrace switch we can observe the target SQL execution

Technical preparationBased on SQL Server2008R2, Microsoft uses a simpler case Library (Northwind) for parsing.IntroductionThe so-called index application is in our daily write T-SQL statement, how to use the existing index, then analysis is what we

Nsarray for an ordered set of objects (equivalent to an array)Nsset for object unordered collectionnsdictionary for key-value mappings the above three collection classes are immutable (once initialized, you can no longer dynamically add or remove