clustered-index

问题 My schema is : CREATE TABLE friends ( userId timeuuid, friendId timeuuid, status varchar, ts timeuuid, PRIMARY KEY (userId,friendId) ); CREATE TABLE friends_by_status ( userId timeuuid, friendId timeuuid, status varchar, ts timeuuid, PRIMARY KEY ((userId,status), ts) )with clustering order by (ts desc); Here, whenever a friend-request is made, I'll insert record in both tables. When I want to check one to one status of users, i'll use this query: SELECT status FROM friends WHERE userId=xxx

问题 I had executed the following procedure in SSMS: CREATE Procedure [dbo].[MyTableLoadByPK] ( @MyTableID int ) AS BEGIN SET NOCOUNT ON SELECT * FROM [MyTable] WHERE del = 0 AND MyTableID = @MyTableID END exec MyTableLoadByPK @MyTableID=1001 MyTable is having 40000 records and there is a clustered index on MyTableID . The STATISTICS IO were same every time I called the above procedure logical reads 2, physical reads 2 : Table 'MyTable'. Scan count 0, logical reads 2, physical reads 2, read-ahead

问题 I am designing forum database using InnoDB and got few questions , Could any one please help me to clarify them? Posts and Comments table design below CREATE TABLE `my_posts` ( `forum_id` mediumint(8) unsigned NOT NULL, `post_id` int(10) unsigned NOT NULL, // not an auto increment subject varchar(200) NOT NULL, `details` text NOT NULL, `access` tinyint(3) unsigned NOT NULL, //private,friends,public `created_by` int(10) unsigned NOT NULL, `created_on` int(10) unsigned NOT NULL, `updated_on`

问题 I have found umpteen posts which begin like Quite a lot of time I have come across people saying "Clustered Index Physically sorts the data inside the table based on the Clustered Index Keys". It's not true! Then such posts go on to describe how it is actually stored, via linked lists or whatever. For example, this post says that Each Index row contains a Key value and a pointer to either an Intermediate level page in the B-tree, or a Data row in the Leaf level of the Index. The Pages in each

问题 I use H2 database for environmental data which contains lots of time series. Time series are simply measurement values of sensors which are recorded in database periodically (say once per hour). The data stored in the table: CREATE TABLE hydr (dt timestamp ,value double ,sensorid int) I would like to make range queries against the table, for example: select * from hydr where dt between '2010-01-01' and '2010-10-01' In order to improve performance I would like to build clustered index over dt

问题 I've got a very simple table which stores Titles for people ("Mr", "Mrs", etc). Here's a brief version of what I'm doing (using a temporary table in this example, but the results are the same): create table #titles ( t_id tinyint not null identity(1, 1), title varchar(20) not null, constraint pk_titles primary key clustered (t_id), constraint ux_titles unique nonclustered (title) ) go insert #titles values ('Mr') insert #titles values ('Mrs') insert #titles values ('Miss') select * from

问题 We are trying to setup an Azure Database Sync group to replicate our data from an on-premise server to an Azure SQL database. This as a first step for a migration to Azure. The Sync Group and Sync Agent have all been set up. When we press the 'Sync' button we receive following error: Trigger Sync Failed: Failed to perform data sync operation: Table '[dbo].[DocumentTypeDocumentVariables]' do not have clustered index. This table did not have a clustered index but an unclustered unique primairy

问题 PostgreSQL has a CLUSTER command that can defrag the data on-demand rather than automatically which kills write speed. Can Firebird CLUSTER on demand? (I can't find it in the docs, and google searches come up well short. Pretty cars tho) 回答1: There is no such command for Firebird (which is also the reason you can't find it). Firebird doesn't have clustered indexes, and doesn't have a way to 'fake' them like PostgreSQL does. 来源： https://stackoverflow.com/questions/19389228/cluster-command-for

问题 I'm having some troubles to deal with a very big table in my database. Before to talk about the problem, let's talk about what i want to achieve. I have two source tables : Source 1: SALES_MAN (ID_SMAN, SM_LATITUDE, SM_LONGITUDE) Source 2: CLIENT (ID_CLIENT, CLATITUDE, CLONGITUDE) Target: DISTANCE (ID_SMAN, ID_CLIENT, SM_LATITUDE, SM_LONGITUDE, CLATITUDE, CLONGITUDE, DISTANCE) The idea is to find the top N nearest SALES_MAN for every client using a ROW_NUMBER in the target table. What I'm

问题 I came across this post in Stackoverflow. The first answer mentions something like A clustered index has all the data for the table while a non clustered index only has the column + the location of the clustered index or the row if it is on a heap (a table without a clustered index). How can a non-clustered index have the location of the clustered index? It only contains the column values sorted as nodes in a B-treee with each node pinting to the row where the column has that node-value,