A database structure that can improve the speed of queries at the cost of disk space and slower inserts/updates. It stores a copy of one or more columns but structures the data differently to allow for faster access.

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MySql INNER JOIN doesn't use composite index

I have two tables, table A which contains date and name of table B entry and table B which contains its name and type. Table a has a composite index on table_b_name and date. I'm selecting all table A ...
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Error when creating an index in SQL Server 2012

I'm trying to create the following index on our test environment (SQL Server 2012): CREATE NONCLUSTERED INDEX [iTransaction-OriginatingTransaction] ON [dbo].[Transaction] ( ...
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1answer
414 views

Does MySQL reindex on update

I have a users table with various fields which are getting updated frequently. i.e table have: userid - PRIMARY int profile_views - int ratings - int last_active - int ( to store UNIX timestamps for ...
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35 views

Error creating spatial index sqlserver

I am creating spatial index on sqlserver table. CREATE SPATIAL INDEX [SIndex_udt_cell_SP_GEOMETRY] ON [udt_cell] ( [SP_GEOMETRY] )USING GEOMETRY_GRID WITH ( BOUNDING_BOX =(80.0713, 26.389581, ...
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Is it possible to optimize a range query so an explain statement would state “using index” instead of “using index condition”?

I have a very large table where specific queries made by my application are timing out. The table looks something like this: LargeTable ------------ Id [BIGINT(20)] UtcTimestamp [BIGINT(20)] Pivot ...
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93 views

How to minimize the need for recalculating index on SQL Server?

We have rather big tables (500 mils rows) where we expect frequent inserts. The tables have approx. 2 indexes each. The problem is that we are afraid that, when the index is recalculating the whole ...
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3answers
107 views

Are these indexes redundant?

I have two indexes on a table that will contain roughly 10-20 million records at a given moment. Index 1 CREATE NONCLUSTERED INDEX [IX_NC_AccountNumber_UTC] ON [dbo].[LogWindow] ( ...
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74 views

Rebuilding index

I have a transaction database and one of nightly job is to rebuild indexes that followed by a log backup and then shrink the log. Is this safe to do so ? Thanks Antony
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I have to create INDEX but which? [closed]

I have to create INDEX but which with this query ? SELECT * FROM TABLE WHERE A = 1 AND B = '5427dbfac0a8280d74bc672c72636a4f' AND C = 'BIL' AND D = 'B' and E = '01' GROUP BY F,G,E,H,I ORDER ...
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91 views

Fill Factor Setting and Performance

From what I've read, typically for indexing the recommendation is to leave the fill factor at 70-80, and the logic behind this seems that new data may be inserted into a table between existing values ...
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2answers
826 views

MySQL not using indexes when joining against another table

I have two tables, the first table contains all articles / blog posts within a CMS. Some of these articles may also appear in a magazine, in which case they have a foreign key relationship with ...
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71 views

Using an enum index to limit records

A common issue, just not sure on the keywords. I have a table of assessments (14k+ records). Each assessment can be in many different states ('draft', 'proofing', 'amends', etc... and 'done'). Most ...
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How to speed up query on table with millions of rows

The Issue: I'm working on a big table that consists about 37mln rows. Data include measurements of many devices made in certain time e.g. '2013-09-24 10:45:50'. Each day all of those devices are ...
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1answer
44 views

Creating Multiple Indexes on SQL Server [closed]

I am creating multiple indexes on a table in SQL Server. The script is still executing but all the required indexes are showing as objects in Object Explorer. Do the objects get created before the ...
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2answers
2k views

What is difference between primary index, secondary index, unique index and normal index?

I work on Oracle systems where I two type of indices exists in any table: Unique index (Based on any search key which is unique key). Normal index (Index made on any search key which is not ...
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1answer
80 views

How to store values of all columns in an index in PostgreSQL?

As described here: https://devcenter.heroku.com/articles/postgresql-indexes#managing-and-maintaining-indexes indexes do not store the entire row data themselves. Is it possible to store the whole row ...
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2answers
113 views

Optimize query or model, to get an population overview in time

I think I've got a very simple model and query, but I cannot find a way to make use of indexes to boost performance. I wonder if there is a trick in my model, or MySQL query, to speed up the ...
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87 views

Is this compound index unnecessary?

I have a large table which contains sensor data, along with the fields: sensor_id timestamp I do queries against it using these fields almost exclusively. There are multiple sensors, and different ...
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1answer
602 views

Improve speed of index rebuild on SQL server

I'm importing a large amount of data into an empty database, and before I start I disabled all non-unique non-clustered indexes to see if I could improve the performance of the import. Now I want to ...
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1answer
566 views

Find the size of each index in a MySQL table

I am trying to figure out size of each index of a table. SHOW TABLE STATUS gives "Index_length" is the summation of all the indices of the table. However if a table has multiple indices (e.g. in an ...
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2answers
137 views

How to improve performance if index is not Most SELECTIVE?

As per suggestion index must be most selective to improve the performance. As a general guideline, we should create indexes on tables that are often queried for less than 15% of the table's rows The ...
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1answer
335 views

MSG 666 when running an insert query on 80M-row indexed table

Strangely, my stored procedure started to receive Msg 666 for some input data. Stored procedure fails on the last step when it tries to insert a row into a table with the following structure: ...
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1answer
96 views

MySQL looking up more rows than needed (indexing issue)

In our MySQL 5.5 database, we have following InnoDB table with 30M+ rows: +----------------+-------------+-----------------+--------+ | participant_id | question_id | given_answer_id | status | ...
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table scheme definiation it this way that insert duplicate into another table

I have a table in which there is a column name with SP varchar(10) NOT NULL. I want that column always to be unique so i created unique index on that column . My table schema as follows : CREATE ...
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1answer
88 views

Combining multiple left join for one single line

We have a query as below. SELECT tblSData.header, tblEAlert.eMessage FROM tblSData LEFT JOIN tblEAlert ON tblSData.sDataID=tblEAlert.sDataID Where tblSData.aID=".$aID." Order By tblSData.dateTimer ...
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95 views

Benefit to keeping a record in the database, rather than deleting it, for performance issues?

So I have a client that I am building a Rails app for....I am using PostgreSQL. He made this comment about preferring to hide records, rather than delete them, and given that this is the first time I ...
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Does a re-index update statistics?

I've been doing the MS10775A course this past week and one question that came up that the trainer couldn't answer reliably is: Does a re-index update the statistics? We found discussions online ...
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172 views

Find missing indexes

tool available to find missing indexes in mssql 2008 ? can we find the missing index using Database Engine Tuning Advisor
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252 views

Unable to drop non-PK index because it is referenced in a foreign key constraint

I have a table named MyTable. The primary key is an identity int column named MyTableID. There is a unique clustered index on the PK column MyTableID named PK_MyTable. I noticed there is an ...
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2answers
158 views

Optimize simple query using ORDER BY date and text

I have a query to a table in Postgres with an order based on a date field and a number field, this table has 1000000 records The data types of the table are: fcv_id = serial fcv_fecha_comprobante = ...
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1answer
48 views

Optimizing a union query

SELECT id FROM user WHERE id IN ( 2,3,4,7,9,21,23,45,324,12,43,254 ) UNION SELECT DISTINCT user_id FROM workgroup_users WHERE workgroup_id IN ( 1,345,34,654,213,123,5,2,3,4 ) I know we should not ...
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216 views

SQL Server 2008 - Question about index behaviour

I have a general question about advanced issues regarding index behaviour. In short, roughly one year ago, we dynamically dropped and recreated a number of indexes with different filters, but using ...
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92 views

How does MySQL or PostgreSQL deal with multi-column indexes in ActiveRecord?

I'm creating indexes for my models right now and I want to know how MySQL and PostgreSQL deal with an index with more than 1 column like: add_index :users, [:username, :created_at] That should ...
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69 views

Understanding multiple indexes with MySQL (and performance)

I have a "phones" table with around 120 000 records, it contains phone_id, phone_number, phone_user_name, phone_last_contacted, etc. The phone_id is index and looks like: 1,2,3,4 ... 120 000. But I ...
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3answers
2k views

Why does MySQL ignore the index even on force for this order by?

I run an EXPLAIN: mysql> explain select last_name from employees order by last_name; +----+-------------+-----------+------+---------------+------+---------+------+-------+----------------+ | ...
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169 views

How to index for a query with independent range conditions?

What is the best way to index a table that I query using independent range conditions? E.g. WHERE X < ? and Y > ?
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216 views

MySQL MyISAM index causes query to match no rows; indexes disabled, rows match

I created a table and index as described in this SE post, but when I query the table for a particular ID, no matches are found. When I disable the index, matches are found. Commands ran: CREATE ...
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1answer
318 views

How to partition an Oracle table with 65 million rows?

The table that needs partitioning contains a list of Components and their Values. So one table is tblComponents. Another is tblFields. Then this table, tblValues, contains the values of the ...
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268 views

how to explain indexes

This question is about teaching: When I learned databases, we talked about indexes being like the card catalog in the town library. We had at least an author index, a title index, then the Dewey ...
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1answer
188 views

Index for speeding up sorting by boolean, timestamp

For a website that displays recent news, I have this query on the home page: SELECT * FROM "cms_news" WHERE NOT ("cms_news"."timestamp" >= '2013-08-08 13:32:39.778988+00:00') AND ...
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Fulltext search returning too many rows

Server: MySQL 5.1.66-0+squeeze1 My problem: I have two databases with the same tables. One is for the testing environment and one for production. When I perform a MATCH AGAINST on the prodution ...
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1answer
101 views

In MySQL if column X has unique values what's the difference between UNIQUE index and B-Tree index

Let's assume that I have table data: CREATE TABLE `test`.`data` ( `row_id` INT NOT NULL , `data_id` INT NOT NULL , PRIMARY KEY (`row_id`) ); Now, let's assume that data_id has unique values. Is ...
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2k views

Index for date column for range query in Oracle?

We have a lot: select count(*) from TBL where XDATE between ? and ? and FLD = ?; We expect to boost performance by tuning index on XDATE column (which have DATE type). What type of indexes more ...
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78 views

Full text catalog does not allow me to hit on singular forms

I have created a full text catalog for a column under database name -> "Storage" -> Full Text Catalogs. It is accent sensitive and "default catalog" is set to false. The language for the column ...
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0answers
198 views

PostgreSQL index array of int4range using GIN / GIST - custom operator class

Here is my table: CREATE TABLE mytable ( id INT NOT NULL PRIMARY KEY, val int4range[] ); I want to index the val column: CREATE ...
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1answer
66 views

What indexes to add on MySQL table

I've been trying to optimize my table, but am yet unable to get the desired results. CREATE TABLE IF NOT EXISTS `puzzles` ( `puzzleID` int(7) NOT NULL, `puzzleMask` varchar(30) CHARACTER SET utf8 ...
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2answers
153 views

Adding an index to a system catalog in Postgres

I'm having a situation very similar to the one described here: I've got a SaaS situation where I'm using 1000+ schemas in a single database (each schema contains the same tables, just different ...
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552 views

MySQL Cluster - Table is full [Error 1114] while still creating tables

I am trying to forward engineer a MySQL Workbench model with about 100 tables to a development single-node cluster and, while creating the 51th table, I end up getting a "1114 table is full" error, ...
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324 views

Avoiding a sort on an already clustered index for group by

On a table T with two fields, pid and did, the following query results in a seq. scan followed by a sort on pid: select count(did), pid from T group by pid Here is the query plan: ...
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LIKE uses index, CHARINDEX does not?

This question is related to my old question. The below query was taking 10 to 15 seconds to execute: SELECT [customer].[Customer name],[customer].[Sl_No],[customer].[Id] FROM [company].dbo.[customer] ...