what is table index

Indexes are the main means to accelerate table content access, especially for queries involving connections to multiple tables. This is an important part of database optimization. We need to understand why indexes are needed, how indexes work, and

The index is created to reduce the time required to retrieve data and improve the retrieval efficiency. If you have created an index and all the indexes are working, but the performance is still poor, it is likely that the index fragmentation is

Document directory Differences between MySQL versions Differences between MySQL versions   MySQL is an open-source relational database management system. The developers are MySQL AB in Sweden, which was acquired by Sun and finally merged into

ProblemARM-LINUX-GCC compiled executable file clkctl, downloaded to the board, under Linux can not run:./clkctl:line 1:syntax Error:word Unexpected (expecting ")")"Resolution Process"1. There are also people on the web who are experiencing this

Cause: It's too slow to make count (*) statistics on the InnoDB table, so find a way to see if it's going to be faster. Phenomenon: First look at a few test cases, as follows First, the test on the Sbtest table Show CREATE TABLE Sbtest\g1. Row ***

The so-called index is a specific MySQL field for some specific algorithm sorting, such as the two-fork tree algorithm and hashing algorithm, the hash algorithm is established by establishing the eigenvalues, and then based on the characteristics of

☆ Database----containers for storing dataThe primary function of a database is to save data.The storage structure of the database---how the data is stored in the database The storage structure of the ☆oracle database:Logical storage structure: How

In the daily study of the database, we found that the default temporary table space of the company production database is up to 30G, the utilization rate is 100%, and the usage rate is 100% after being adjusted to 32G, which causes the disk space

On the two-piece algorithm learning: 1 recursive algorithm of divide and conquer strategy2) recursive algorithm of merge ordering The previous study introduced a recursive algorithm in the ranking of an application: merge sort, in the ranking

1. DIRECTORY Specify the directory where dump files and log files are locatedDirectory=directory_objectDirectory_object is used to specify the directory object name. Note that directory objects are objects created using the Create DIRECTORY

 The parallel (Parallel) operational feature is a technical feature of Oracle to make full use of server hardware processing resources, improve the operation efficiency of certain large amount of data, and deal with mass production data.

The types of elf files under Linux are divided into the following ways: 1, can reposition files, such as SIMPLESECTION.O; 2, executable files, such as/bin/bash; 3, share the target file, such as/lib/libc.so. In the next article, we'll use

One, C + + customers reuse C + + objects Suppose you already have a class that you can reuse, we can reuse it in our own program, just add its definition and implementation file to our own project, and include this type of definition file in the

A basic table new two tables: Table1 and table2 Table 1 (id,uid,name), the UID is a set of foreign keys, the foreign key does not have to set the automatic self increase and unsigned place do not draw √. ID as the primary key, set to self increase.

Relational table type, which is a very powerful type. We can think of this type as an array. Just an array of C languages, which can only be indexed by a positive integer; in Lua, you can use any type of valueTo count the index of the group , but

EXPLAIN as a DB2 query plan, generally need to open their own, but generally run DB2-TVF EXPLAIN. DDL but I've been running a lot of times and it's been wrong. Because it is not in the same directory, there will be an error. It should be written

friends who need to learn can be downloaded via the Web: http://tadown.com/fs/byib0ens3hu207015/Content Profile ...This book, through a large number of examples, explains in detail the fundamental changes in the way of thinking that must be faced to

This note will describe the nature and interrelationships of the logical storage structure in the Oracle database server in the segments, regions, and blocks.1. Introduction of data segments, sections and segments2. Overview of paragraphs3. District

local_db installed in SuSELOCAL_DB's Tnsname(DESCRIPTION = (ADDRESS = (PROTOCOL = TCP) (HOST = 192.168.31.110) (PORT = 1521))(Connect_data = (SERVER = dedicated) (service_name = ora11g)))1. Built Dblink connected to remote_dbCREATE DATABASE LINK Win7

First, the Export method:There are four ways to export data using the Exp/imp method:1. Table mode export: One or more specified tables, including the table definition, table data, table owner authorization, table index, table constraints, and