Get the SUM of one column when grouped by another column in SQL

Question

I have a table with 3 fields

ID  Tax   State
0   .50   TX
1   .25   TX
2   .25   AZ
3   .25   AZ
4   .1    AL

I want to pull the sum of Tax for each state.

Tax   State
.75   TX
.5    AZ
.1    AL

How would I write a query to do this?

Answer 1

This is a really rudimentary SUM() aggregate. I recommend reading your RDBMS' documentation on aggregate functions and GROUP BY because this is quite elementary.

SELECT
  SUM(Tax) AS sumtax,
  State
FROM table
GROUP BY State
/* Looks like you want descending order */
ORDER BY SUM(Tax) DESC

Note that some RDBMS (MySQL, for instance) will allow you to use a column alias in the ORDER BY as in:

ORDER BY sumtax DESC

... where others (Like SQL Server if I recall correctly) will not and you must use the aggregate value there too.

Edit: I just checked and actually SQL Server does seem to allow aliases in the ORDER BY. Pretty sure you can't use an alias in the GROUP BY though...