SQL YTD for previous years and this year

Question

Wondering if anyone can help with the code for this. I want to query the data and get 2 entries, one for YTD previous year and one for this year YTD.

Only way I know how to do this is as 2 separate queries with where clauses.. I would prefer to not have to run the query twice.

One column called DatePeriod and populated with 2011 YTD and 2012YTD, would be even better if I could get it to do 2011YTD, 2012YTD, 2011Total, 2012Total... though guessing this is 4 queries.

Thanks

EDIT: In response to help clear a few things up: This is being coded in MS SQL.

The data looks like so: (very basic example)

Date       |   Call_Volume
1/1/2012   |   4

What I would like is to have the Call_Volume summed up, I have queries that group it by week, and others that do it by month. I could pull all the dailies in and do this in Excel but the table has millions of rows so always best to reduce the size of my output.

I currently group by Week/Month and Year and union all so its 1 output. But that means I have 3 queries accessing the same table, large pain, very slow not efficient and that is fine but now I also need a YTD so its either 1 more query or if I could find a way to add it to the yearly query that would ideal:

So

DatePeriod   |   Sum_Calls
2011 Total   |   40
2011 YTD     |   12
2012 Total   |   45
2012 YTD     |   15

Hope this makes any sense.

Answer 1

SQL is built to do operations on rows , not columns (you select columns, of course, but aggregate operations are all on rows).

The most standard approach to this is something like:

SELECT SUM(your_table.sales), YEAR(your_table.sale_date)
FROM your_table
GROUP BY YEAR(your_table.sale_date)

Now you'll get one row for each year on record, with no limit to how many years you can process. If you're already grouping by another field, that's fine; you'll then get one row for each year in each of those groups.

Your program can then iterate over the rows and organize/render them however you like.

If you absolutely, positively must have columns instead, you'll be stuck with something like this:

SELECT SUM(IF(YEAR(date) = 2011, sales, 0)) AS total_2011,
  SUM(IF(YEAR(date) = 2012, total_2012, 0)) AS total_2012
FROM your_table

If you're building the query programmatically you can add as many of those column criteria as you need, but I wouldn't count on this running very efficiently.

(These examples are written with some MySQL-specific functions. Corresponding functions exist for other engines but the syntax would be a little different.)