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MySQL index details, MySQL index detailsI. Introduction to index basics 1.1 In MySQL, indexes are also called keys. They are a data structure that the storage engine uses to quickly find records. Indexes are critical to good performance. Especially

This article is transferred from: Http://www.cnblogs.com/abcdwxc/archive/2007/12/11/990274.html ----------------------- Creates an index for a given table or view.Only the owner of a table or view can create an index for the table. The owner of a

ReprintedBytes IndexYou can use indexes to quickly access specific information in database tables. An index is a structure that sorts the values of one or more columns in a database table (for example, the last name (lname) column of the employee

SYS. dm_exec_requests is a powerful tool to check the performance bottleneck of SQL Server. Update statistics t_goods with fullscan --- Update table statisticsThe index leaves of clustered indexes are the data itself.The leaf node of the

Unique indexIf the primary key is not set to a clustered index when it is created, it must be a unique nonclustered index. In fact, the unique index, the name Incredibles, is that it requires the value on that column to be unique. A unique index

062 Creating an indexIndexing is especially important for queries that are the primary application. A lot of times the performance problem is simply because we forgot to add an index, or we didn't add a more efficient index. If you do not index,

Understanding MySQL-index and optimization summary, mysql Index Summary Preface: indexes have a crucial impact on the query speed. Understanding indexes is also the starting point for optimizing database performance. Consider the following: Assume

First, Introduction1. What is an index?General application system, reading and writing ratio of about 10:1, and the insertion operation and the general update operation rarely appear performance problems, in the production environment, we encounter

B-tree index access When an oracle process needs to access data blocks in a data file, Oracle has two types of I/O operations: 1) Random Access: Read a data block each time (represented by the "DB file sequential read" Wait event ). 2)

1.oracle OptimizerThe goal of optimization is divided into 4 categories:Choose (optional)Rule (rules-based)First rows (line one)All rows (all rows)Description: Describe the execution plan for SQLObject owner: Objects SchemaObject Name: Objects