how to improve query performance

In the previous article "Supplement to SQL query optimization -- (in)", we mainly discussed the query statements such as select... from... where... in. Next, let's discuss Select... from... where... exists. The query speed of exists is much higher

Required SkillsSkill Requirements:Data IngestData digestion:The skills to transfer data between external systems and your cluster. This includes the following:The ability to transfer data between external systems and clusters, including the

Https://cwiki.apache.org/confluence/display/solr/Nodes%2C+Cores%2C+Clusters+and+LeadersNodes and CoresIn Solrcloud, a node was Java Virtual machine instance running SOLR, commonly called a server. Each SOLR core can also is considered a node. Any

The value of the AttributeHierarchyEnabled property determines whether the attribute hierarchy is created. If this property is set to False, the attribute hierarchy is not created, and the property cannot be used as a level in the user hierarchy,

First, preface The first 4 elasticsearch usage of the API and the principle of things introduced a bit, I believe that we have a certain understanding of elasticsearch, and then we mainly from the establishment of the index to the later stage of

First, index fast Scan (index fast full scan)The index fast full scan, which is very similar to index full scan, is also suitable for all types of B-tree indexes, including unique indexes and non-unique indexes. As with the index full scan, the

Why do you create an index? This is because creating an index can greatly improve the performance of the system.First, by creating a unique index, you can guarantee the uniqueness of each row of data in a database table.Second, it can greatly speed

Define fact relationships : You sometimes need to define the dimension of the measurement value based on the data items in the fact data table, or query other specific information in the fact data table, such as the invoice number related to the

Hide and disable attribute hierarchies:By default, an Attribute Hierarchy is created for each attribute in the dimension in Microsoft SQL Server 2005 Analysis Services (SSAs), and each hierarchy can be used to determine the dimension of the fact

1. dimension is a specific angle for people to observe the topic. Each dimension is described by a table, called a dimension table. It is a detailed description of the dimension. 2. fact indicates the topic of interest. It is also described by a

InSQLServer, the view is a stored T-SQLQuery. View DefinitionSQLServer saves, so that it can be used as a virtual table to simplify queries, and adds another layer of security to the base table. However, it does not occupy any space in the database.

The guidelines to be followed when designing indexes include: Database Rules, query rules, and column rules. Detailed descriptions of each criterion are listed below. Among them, 1-3 belongs to the database criterion; 2-8 belongs to the query

Materialized views are similar to indexes in many aspects: materialized views are used to improve query performance, while materialized views are transparent to applications, adding or deleting materialized views does not affect the correctness and

Convert a long date to a short date Convert (char (10), getdate (), 120) MS-SQL database development commonly used Summary 1. sort by surname strokes: Select * From TableName Order By CustomerName Collate Chinese_PRC_Stroke_ci_as 2. database

  Introduction to solution objects   Schema is a set of Logical Data Structures (or schema objects.Each database user has a solution with the same name. Solution objects can be created and operated through SQL statements.   The object types that can

Materialized views are similar to indexes in many aspects: materialized views are used to improve query performance, while materialized views are transparent to applications, adding or deleting materialized views does not affect the correctness and

  In the previous article (database indexing Principle 1), we elaborated on the basic concepts and data query principles of indexes, we know that when creating an index, we must make a balance between "speeding up the query speed" and "Reducing the

Windows Phone 7 released in March supports data access in the following ways: XML, isolated storage [independent storage], and cloud [cloud storage]. Windows Phone 7 does not have local database APIs available. Windows 7 phone local data storage

I. Preface Index plays an important role in database performance. The advantages and disadvantages of index design directly affect the efficiency of DB execution. Therefore, when performing DB tuning, some of them will start to process the index.

I. theoretical part The Materialized View of Oracle is a database object that includes query results. It is a local copy of remote data or is used to generate a summary table based on the sum of data tables. Materialized View stores data based on