how to improve query performance

1. What is cube? A simple cube object consists of basic information, dimensions, and measurement value groups. The basic information includes the name, default measurement value, data source, and storage mode of the cube. A dimension is an actual

What is an index? Index is an important tool to improve query performance. index is to add a small amount of data required by the query statement to the index page. In this way, you only need to access the pages of a few indexes when accessing data.

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

Although the Oracle system has already provided several techniques for tuning system performance, if the database design itself is problematic, especially in terms of structure, what can you do if you have the power to do? Therefore, it is

Question 1: Why do I need to introduce table variables when a temporary table already exists? Solution 1:Compared with temporary tables, table variables have the following advantages: As described in the SQL Server books online "tables"

Introduction In SQL Server, indexes are enhanced, which means that SQL server can still implement its functions even if there is no index. However, indexes can greatly improve query performance in most cases, especially in OLAP. to fully

Big data processing is a headache, especially when professional DBAs are not ready to use, they feel rogue about some database problems. Therefore, it is necessary to understand some database skills. Of course, everyone has their own database skills,

　1. Batch modification and Deletion In hibernate 2, if you want to modify or delete any data, you must first query the data to be modified or deleted, then perform operations on the data. There is no problem in using this processing method when the

I. database objects: Relational graphs, tables, views, stored procedures, roles, users, rules, default values, user-defined data types, and user-defined functions. Tables are the most basic objects. Tables are used to store physical data. To

According to Microsoft's official message, SQL Server 2014, the next database platform version, will be released by the end of this year. It will include the table-level memory OLTP function, unlike other memory databases, this feature eliminates

Linux Study Notes 2_mysql installation, Study Notes 2_mysql There are many commands for viewing file content: cat, tac, more, less, head, tail, nl. Cat displays the file content from the first line. tac displays the file content from the last line.

Reasonable creation of strategic indexes for database tables can greatly improve query performance. But in fact, the index we create in daily life is not a strategic index. It is precisely because a large number of redundant or useless indexes

121. you want to create a new optimized database for your transactional production environment to be used by a financial application. while creating the database, you want the Oracle software to take care of all basic settings to optimize the

Preface Indexes are one of the most important objects in relational databases. They can significantly reduce disk I/O and logical read consumption and improve the query performance of SELECT statements. However, it is a double-edged sword. Improper

I. B-Tree indexes 1. Principles for selecting index fields: The most frequently used field in the where clause Join fields in a join statement Select highly selective fields (if a few fields have the same value and there are many unique values,

In the Oracle world, you can use: 1) case expression or 2) decode Function To realize logical judgment. Oracle's DECODE function is very powerful. If you use it flexibly, you can avoid multiple scans to improve query performance. CASE is a syntax

MySQL5.7 implement expression indexes for virtual Columns MySQL has not provided such complex functions as function indexing since ancient times. So how can this function be implemented in MySQL? Let's take a look at the concept of function indexing.

1. Index in SQL Server An index is a disk structure associated with a table or view, which can accelerate the speed of retrieving rows from a table or view. An index contains keys generated by one or more columns in a table or view. These keys are

Introduction In SQL Server, indexes are enhanced, which means that SQL Server can still implement its functions even if there is no index. However, indexes can greatly improve query performance in most cases, especially in OLAP. to fully

1. copy only one table structure without copying data Select top 0 * into [t1] from [t2] 2. Obtain the creation script of an object in the database 1. Use the following script to create a function. If exists (select 1 from sysobjects where id =