oex index

[pk_student] PRIMARY KEY CLUSTERED ([ID] ASC) with (Pad_index = off, Statistics_norecompute = off, Ignore_dup_key = off, Allow_row_lock S = on, allow_page_locks = on) on [PRIMARY]) on [PRIMARY] GO ALTER TABLE [dbo]. [Student] ADD CONSTRAINT [Df_student_entrancedatetime] DEFAULT (GETDATE ()) for [Entrancedatetime]go Insert 5 million data into the table: DECLARE @i INT; SET @i=1; while (@i 1. Use indexes reasonably to improve query speedIn the query table, all ages 10 n

Indexing is already a problem that we often mention during performance optimization. Many indexing concepts and resolutions are part of our site's advanced index series.ArticleWe will not repeat it here because we have made a comprehensive introduction. We all know that for indexes, we will face two problems: 1. Have you created an appropriate index? 2. How to maintain and diagnose existing Indexes

One of the pitfalls of indexing using indexes: Leading columns that do not use a composite index cause the query to not use the index In Oracle, we often assume that indexed, SQL queries use the index as we would like, in fact, Oracle only uses indexes under certain conditions, and here we sum up the 1th: Oracle uses indexes when they include leading columns in t

If there is a clustered index and the lookup column is not in the key column of the nonclustered index and the RID lookup bookmark is used in a table that does not have a clustered index, it may be because the overhead is too large to cause some queries to directly perform table scan clustered index all the data is in

Sometimes a long character column needs to be indexed, which will make the index larger and slower. One policy is to simulate hash indexes. But sometimes this is not good enough, then? Generally, you can index the first few characters instead of all values to save space and improve performance. This reduces the size required for the index, but also reduces the s

The index creation rules for mysql optimization and the index Optimization for mysql The data structure commonly used for indexing is B + tree.. The structure is as follows: For example, it is a B + tree. For the definition of B + tree, see B + tree. Here we only talk about some key points. The light blue block is called a disk block, each disk block contains several data items (in dark blue) and pointers

This article is applicable to the reading references of the attacker who has some in-depth knowledge about database indexes. We are easy to understand clustering index scanning and table scanning, but it is not easy to understand non-clustered index scanning. This is often confusing for beginners, the reason is that there is no need for non-clustered index scanni

1, where the query conditions in the sentence is not equal to the number (where column!= ...) ), MySQL will not be able to use the index 2. Similarly, if a function is used in the query condition of the WHERE clause (for example, where day (column) = ...). ), MySQL will not be able to use the index 3, in the join operation (need to extract data from multiple data tables), MySQL can only use the primary key