what is table index

1, the table's primary key, the foreign key must have the index; 2, the data volume of more than 300 of the table should be indexed; 3, often with other tables to connect the table, in the connection field should be indexed; 4, often appear in

Turn from: http://tong7858-126-com.iteye.com/blog/829323 1. In versions above Oracle8, you can use the following statements to index names and queries that create INDEX statements.SELECT index_name,dbms_metadata.get_ddl (' INDEX ',

First create a large table: CREATE TABLE Big_tableAsSelect RowNum ID, a.*From All_objects Awhere 1=0/ALTER TABLE big_table nologging; DeclareL_CNT number;L_rows Number: = &1;BeginInsert/*+ Append * *Into big_tableSelect RowNum, a.*From All_objects A;

Preface: In most cases, a table scan or index scan is not an efficient way to return a small amount of data, especially from a large table. These must be found and resolved to improve performance because the scan traverses each row, finds the

Underlying Implementation of hashmap and underlying implementation of hashmap The underlying implementation of HashMap is implemented by the array + linked list structure. To add, delete, and obtain elements, calculate the hash value based on the

Oracle IMPDP's table_exists_action detailedCategory: [oracle]--[Backup and Recovery]2012-01-06 22:44 9105 People read Comments (0) favorite reports Tableactionoracleschemaobjectimport1 table_exists_action parameter DescriptionWhen importing data

FillCell This method is a recursive method for filling in a Sudoku table. Let's look at the long drop of code:Code Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->/// /// Fill the cell /// ///

The data pump is a server tool, and the exported files are stored on the server where the database is located. Of course, we know that the files can be controlled through directory objects. The directory object has four levels by default. Of course,

1 table_exists_action parameter descriptionWhen importing data using IMP, if the table already exists, drop the table before importing.When using IMPDP to complete the database import, if the table already exists, there are four kinds of processing

Interest-induced research on the source of HashMap, write down their understanding, based on JDK1.8.This article probably analyzes HashMap's put (), get (), resize () three methods.First let's look at the put () method. Public v put (K key, V

Java and java Official Website If you are interested, study the source code of HashMap and write down your understanding based on jdk1.8. This article roughly analyzes the put (), get (), and resize () Methods of HashMap.   First, let's take a look

(Part 1)-------------------4.6 visibility and upvalue-------------------A function body can reference its own local variables (including its parameters) and global variables, as long as they are not hidden by local variables with the same name in

Some time ago in a migration of data pump and exp, found that the difference in efficiency is quite large. Here is an example of a simple comparison. This article discusses the effect of parallelism on the export of data pumps. Write a few

Examples of dictionary and hash table structures that correspond to key values in JavaScript, javascript Dictionary javascript implementationProgramming logic: The raw object datastore is used for element storage; Two methods are implemented to

Chinese character sorting,Hybrid sorting,Data size sorting,Sort file types (suffix names)Date and time sorting,Price sorting,Sort Chinese mixed numbers;Usage: new tableListSort (arguments, arguments) after the document is loaded ).Two parameters are

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Author: skate Time: 2010-08-31   Expdp Test   1. Single process, two Exported Files   C:/Documents and Settings/Administrator> expdp 'sys/Aibo @ test as sysdba 'ctorY = dpdump dumpfile = expdp1.dp, expdp2.dp tables = (skate. testbind, skate.

1. Use expdp and impdp Oracle Database 10 Gb introduces the latest data pump technology, the role of Data Pump Export Import (expdp and impdp) 1) implement logical backup and logical recovery.2) move objects between database users.3) move objects

Introduction Earlier article said, when encountering the high concurrency data storage layer, will first think of read-write separation, while high concurrency may mean that the data volume, a large number of query or update operations concentrated

Commands for dump files include exp/IMP and expdp/impdp. These four commands have been compiled in related articles.   Oracle exp/IMP description Http://blog.csdn.net/tianlesoftware/article/details/4718366   Comparison between exp/IMP and