index key

1, the primary key must be unique, not necessarily the clustered index, we create the primary key by default is to set the primary key is a clustered index. You can re-build the clustered index by manually deleting it.2, the SQL statement is where

Look at a PHP blog today and note that: "The index key value in PHP, if not enclosed in quotes, interprets the index key value as a constant, which is interpreted as a string when no definition of the constant is found." I'm a little bit convinced

Simple IntroductionIn SQL Server, data is stored on a per-page basis. When you add a clustered index to a table, SQL Server looks for the data according to the clustered index column as keyword.Therefore, the impact on the performance of the

One, MySQL data type:1. Numeric Type:integer type: when using the unsigned modifier, only positive values are taken, the value is not sufficient to specify the width, and the left fill spaceInteger types include: Tinyint,smallint,int, etc. Float

One, the structure of the Hash indexThe hash index consists of the buckets set, and index Key is mapped by the hash function, resulting in a hash value, which is filled into the corresponding bucket, and the hash value of each bucket is different.

15. Use Transact-SQL and Enterprise Manager to manage data tablesModifying a data table with a T-SQLUse Enterprise Manager to modify data tablesImpact of modifying a data tableDelete A data tableSummaryIn Chapter 10th, you have learned how to create

I am going to index the fields of a table in SQL server2005 today. The creation fails. Check the table structure. The original field is nvarchar (max) and cannot be indexed.   Later, change this field to nvarchar (4000) and re-execute the create

first, the concept of bookmark searchBookmarks can help SQL Server quickly direct from the nonclustered index entry to the corresponding line, but I can actually say a few words about it.　　If the table has a clustered index (the section structure),

First, the concept of bookmark searchBookmarks can help SQL Server quickly direct from the nonclustered index entry to the corresponding line, but I can actually say a few words about it.　　If the table has a clustered index (the section structure),

first, the concept of bookmark searchBookmarks can help SQL Server quickly direct from the nonclustered index entry to the corresponding line, but I can actually say a few words about it.　　If the table has a clustered index (the section structure),

Before I start, I want to talk about several concepts. Overwrite Query] When an index contains all the columns referenced by a query, it is usually called "Overwrite query ". [Index coverage] If the returned data column is included in the

In SQL Server 2005, you can extend the non-clustered index function by adding non-key columns to the leaf level of the non-clustered index. By including non-key columns, you can create non-clustered indexes that overwrite more queries. This is

Description of pseudo columns and pseudo columns in the SQL Server database. Pseudo columns in SQL Server In the afternoon, someone in the QQ group was discussing (non-clustered) index storage. For clustered index tables, the non-clustered index

Http://www.cnblogs.com/gaizai/archive/2010/01/11/1644358.html   Before I start, I want to talk about several concepts. Overwrite Query] When an index contains all the columns referenced by a query, it is usually called "Overwrite query ". [Index

SQL Server 2005 Books Online (November 2008) index with inclusive columns In SQL Server 2005, you can extend the functionality of nonclustered indexes by adding non-key columns to the leaf level of a nonclustered index. By including Non-key columns,

There are a couple of concepts to talk about before you start."Overwrite Query"When an index contains all the columns referenced by a query, it is often referred to as an "overwrite query.""Index Overlay"If the returned data column is contained in

Pseudo-Columns in SQL ServerQQ Group in the afternoon to see someone in the discussion (nonclustered) index storage,Say, for a clustered index table, the nonclustered index stores the index key value + the clustered index key value; For a

Reading directory (content) 1 Row Records how to store 1.1 Heap Table 1.2 Clustered Index Table 2 Nonclustered index structure 3 Nonclustered index key value contents 3.1 Nonclustered indexes on a heap

In fact, you can understand the index as a special directory, the following article mainly introduces the SQL Server index principle of the relevant information, the text through the sample code introduced in very detailed, to everyone's study or

What is the principle of database indexing? The management of the MIS system for small and medium-sized enterprises is basically composed of two parts: one is the visual operation at the front end, and the other is the database management at the