I am using MySQL 4.0.x on a Linux machine with a JSP/Servlet front-end to
display the data.
I have a table with experimental data for each flight of a rocket.
Conceptually, it looks like (with many more columns):
Flights
+-----------+----------+----------+
| flight_id | data1_id | data2_id |
+-----------+----------+----------+
| 1 | 1 | 1 |
| 2 | 1 | 3 |
| 3 | 1 | 1 |
| 4 | 2 | 2 |
| 5 | 2 | 3 |
| 6 | 1 | 1 |
| 7 | 1 | 1 |
| 8 | 4 | 4 |
| 9 | 1 | 2 |
| 10 | 1 | 2 |
| 11 | 1 | 1 |
+-----------+----------+----------+
The data1_id and data2_id are indexes for the data recorded for that flight.
I want to summarize the data. One such summary is to count the number of
different data1_id's and data2_id's. For example:
Flight Result Summary
index: 1 2 3 4
data1_id 8 2 0 1
data2_id 5 3 2 1
I can think of 2 ways to make this summary table.
1. Issue 4 queries per data_id of the form
SELECT COUNT(flight_id) FROM Flights WHERE data1_id=**
where ** is set to the values 1,2,3,4. For the table above, I would have to
issue a total of 8 queries.
2. Issue one query of the form
SELECT flight_id FROM Flights
and do the counting in my Java code. A simple loop through the ResultSet could
count the different values for the data_ids.
My questions are:
1. Is there a better way than these two options for getting the data I want? A
single query per data_id?
2. Generally, what is the most "efficient" way to do this? Is is better to
issue more queries that gather the "calculated data" or better to issue one
query for the raw data and then do the calculations in Java? I am sure there
are many factors that effect the answer to this question - server resources,
code design, etc. However, I am interested in a best practices type of answer
or general rule of thumb from the sage experts on the list.
Thanks for any insights you can provide!
--
Mark Phillips
Phillips Marketing, Inc
[EMAIL PROTECTED]
602 524-0376
480 945-9197 fax
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