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.
38
votes
4answers
2k 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 ...
36
votes
4answers
6k 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 ...
19
votes
7answers
4k 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 ...
4
votes
2answers
409 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 ...
2
votes
2answers
501 views
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 want to have the following view
CREATE OR REPLACE VIEW daily_trans ...
6
votes
2answers
497 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, ...
5
votes
2answers
639 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)
, ...
4
votes
1answer
980 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 ...
