Combining multiple data points into a single data point. This usually is used in reference to SQL and usually to an aggregate function of some sort.

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0
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2answers
97 views

Grouping data checking against top values

I've got data in this form: CallNum Value Accepted -------------------------------------- 971374 81.482204444473609 True 971374 83.783551111089764 False 971374 97.936875555547886 ...
1
vote
1answer
843 views

ORDER BY on aggregate field on a closure table giving unexpected results

I am updating my companies product database and I'm looking into different ways to do design our faceted navigation "selector" tables. The idea of faceted navigation might look like this: It's ...
19
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3answers
5k views

Why does ANSI SQL define SUM(no rows) as NULL?

The ANSI SQL standard defines (chapter 6.5, set function specification) the following behaviour for aggregate functions on empty result sets: COUNT(...) = 0 AVG(...) = NULL MIN(...) = NULL MAX(...) = ...
3
votes
2answers
843 views

Pivoting data for stacked charts (grouping and creating new columns for each distinct value)?

I have something that looks like this (SQL Fiddle here): Date Location Value 1/1/2012 Baltimore 36 1/1/2012 Houston 36 1/1/2012 Chicago 55 2/1/2012 Baltimore 49 ...
5
votes
1answer
820 views

Is it possible to wrap aggregate functions in Postgres?

Postgres' string_agg(expr, delimiter) function is great. But I would like to have a version that takes a single argument -- the field to aggregate -- and assumes a delimiter of ', ' since that is ...
24
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7answers
29k views

What is the most efficient way to get the minimum of multiple columns on SQL Server 2005?

I'm in a situation where I want to get the minimum value from of 6 columns. I've found three ways so far to accomplish this, but I have concerns with the performance of these methods and would like ...
1
vote
2answers
915 views

LIMIT to one row per ID

This query gives me multiple hits because of each assetid may contain many vb.title. How can I limit the result to only 1 hit for each assetid? 'select DISTINCT v.id, v.purchasedate, ...
3
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1answer
731 views

Is it possible to make a reference to the result of an aggregate function in a SELECT clause from the same SELECT clause?

I'm not a Database Administrator--just a Software Engineer. I would like to know if it is possible to reduce the following T-SQL query: SELECT SUM(Price * Quantity) as 'Total', SUM(Price * ...
3
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3answers
5k views

How do I create a user-defined aggregate function?

I need an aggregate function that MySQL doesn't provide. I would like it to be in MySQL's flavor of SQL (that is, not in C). How do I do this? What I'm stuck on is creating an aggregate function -- ...
2
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1answer
724 views

Performing aggregations and calculations: SQL (CTE) vs MDX

I’ve hit a wall and would like some expert advice. I’m building a data warehouse and don’t quite understand whether the calculations (also time aggregations) should be done in SQL (T-SQL and CTE) or ...
2
votes
4answers
5k views

Should I use the Infobright database or is there a better aggregation solution?

We are a MySQL front-end shop and have a system currently logging event data in a highly structured format. Think apache traffic log. We need to be able to aggregate counts of this data (cube) vis a ...
11
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3answers
12k views

Why is an aggregate query significantly faster with a GROUP BY clause than without one?

I'm just curious why an aggregate query runs so much faster with a GROUP BY clause than without one. For example, this query takes almost 10 seconds to run SELECT MIN(CreatedDate) FROM MyTable WHERE ...
2
votes
1answer
949 views

Why use custom CLR aggregate functions for string concatenation and geometry unions in SQL Server?

I often need to do string concatenation or geometry unions over a column in SQL Server 2008 and I'm aware that you can write custom aggregate functions in .NET and register them with SQL Server to do ...
2
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1answer
1k views

Calculate percentage of false records to total records within a aggregate function

I'm looking for a solution to calculate a percentage rate of a boolean value: Model: Products 1 <-> n Components Components.essential is a boolean attribute What I want to calculate ...
6
votes
2answers
5k views

PostgreSQL query with max and min date plus associated id per row

I have the following table: CREATE TABLE trans ( id SERIAL PRIMARY KEY, trans_date date, trans_time time ); I want to have the following view CREATE OR REPLACE VIEW daily_trans ...
0
votes
0answers
48 views

postgresql view [duplicate]

Possible Duplicate: postgresql view with max min with id I have the following table: CREATE TABLE trans ( id SERIAL PRIMARY KEY, trans_date date, trans_time time ); I ...
6
votes
4answers
600 views

Find the first gap in an aggregation of integers in SQL Server

Let's say I have a table called dbo.GroupAssignment. GroupID | Rank ------------------ 1 1 1 2 1 3 2 1 2 3 2 4 3 2 3 4 3 5 The PK is GroupID, Rank. Normally, the ranks ...
4
votes
2answers
254 views

MySQL aggregate anomaly

I was checking selectivity of some columns for an index. Where is this "ignore what I give you" behaviour documented? This gives 4,851,908, 4,841,060, and 1,000,052 SELECT COUNT(*), ...
34
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7answers
23k views

Writing a simple bank schema: How should I keep my balances in sync with their transaction history?

I am writing the schema for a simple bank database. Here are the basic specifications: The database will store transactions against a user and currency. Every user has one balance per currency, so ...
2
votes
3answers
353 views

Non-deterministic aggregated result

Why is my query non-deterministic? I have query that do the following: select sum(float1*float2*coalesce(float3,1)) from table When I run this query I get a deterministic result, but it seems not ...
4
votes
2answers
15k views

SQL query that concatenates values from duplicate rows in a single table

Let's say I have a table of employees, like this: Name Sex Role Bob M Developer Joe M QA Now, I have a problem with duplicated rows in this table. I will fix it ...
5
votes
2answers
957 views

Is it a good idea to split MySQL DB into two servers

I have a MySQL DB server that accepts a lot of mobile application data for analysis. I would like to know if for optimization reasons the following architecture makes sense and is appropriate: I ...
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2answers
1k views

Using totals on aggregates to improve performance

I have two tables: details and totals of these details. Details (Slow solution): select OrderId = r.OrderId , TotalQty = SUM(r.Quantity) , ...
17
votes
5answers
43k views

How can I use a default value in a Select query in PostgreSQL?

I would like to use a default value for a column that should be used if no rows is returned. Is that possible in PostgreSQL? How can I do it? Or is there any other way I can solve this? E.g. ...
6
votes
2answers
691 views

Most efficient way to return multiple aggregates in a single stored proc?

What is the best or most efficient way to get multiple aggregate result values? Basically I have an email app and wanted to get all the numbers of messages for each type of folder (inbox, sent, ...
49
votes
4answers
23k views

What is the difference between select count(*) and select count(any_non_null_column)?

I seem to remember that (on Oracle) there is a difference between uttering select count(*) from any_table and select count(any_non_null_column) from any_table. What are the differences between these ...
4
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2answers
1k views

MAX for each subset

I have a table that looks like this: +---------------------------------------------+ | EVENT_ID | ITEM_ID | PERSON_ID | EVENT_DATE | +---------------------------------------------+ | 123 | 1 ...
4
votes
1answer
2k views

How do I horizontally partition an oracle database table, and should I?

We have a tenanted data warehouse that we are doing reporting on. Queries are beginning to take a long time, and we're looking at options to reduce this. There are two thoughts at the moment. Create ...
28
votes
13answers
77k views

Eliminate duplicates in ListAgg (Oracle)

Prior to Oracle 11.2 I was using a custom aggregate function to concatenate a column into a row. 11.2 Added the LISTAGG function, so I am trying to use that instead. My problem is that I need to ...
9
votes
3answers
38k views

Calculating percentage of a row over total sum

Apologies for the bad title, I wasn't sure what would be a good title for this. This is currently (simplified view of the) data I'm working with Agent | Commission ---------|------------ ...
61
votes
4answers
11k views

Storing vs calculating aggregate values

Are there any guidelines or rules of thumb to determine when to store aggregate values and when to calculate them on the fly? For example, suppose I have widgets which users can rate (see schema ...