Combine two select statements in one SQL statements

Question

I have the following two queries that I need to combine into one query, where it updates a single row at the same time.
SELECT count(*) FROM database.USAGE WHERE SERVICE_TYPE = 'C' AND ACCOUNT = "4837"
SELECT sum(minutes) FROM database.USAGE WHERE SERVICE_TYPE = 'DA' AND ACCOUNT = "4837"
I want to insert the values of each select statement into two columns of the same row, as well as insert the account number from the select statement.
After the query has been executed, the database row will look like this:
ACCOUNT COUNT SUM
4837 354 1039202
I am looking for suggestions on how to:
- either combine the two into one query
- simply update each column with the value from each query by updating the row with the account value
I am a SQL newbie - so I appreciate any assistance.
Thanks,
Tony

Answer 1

Hi, Tony,
When you're talking about changing the data in tables, "INSERT" means to add a new row, and you'll cause a lot of confusion if you use it to mean something else. So don't say
"I want to insert the values of each select statement into two columns..."; use some other word, like:
"I want to put the values of each select statement into two columns ..."
If you happened to know that those two numbers were 354 and 1039202, you might say:
UPDATE  table_x
SET     a_count = 354
,       a_sum = 1039202
WHERE   account = 4837;But you don't know the numbers; you want to have the query figure out what they are.
In most places where you can use a literal (like 354 or 1039202), you can also use a scalar sub-query, a SELECT statement, enclosed in parentheses, that produces one column and (at most) one row.
In your case, you can say:
UPDATE  table_x
SET     a_count = (SELECT count(*) FROM database.USAGE WHERE SERVICE_TYPE = 'C' AND ACCOUNT = 4837)
,       a_sum = (SELECT sum(minutes) FROM database.USAGE WHERE SERVICE_TYPE = 'DA' AND ACCOUNT = 4837
WHERE   account = 4837;or, to make it more readable:
UPDATE  table_x
SET     a_count =
( SELECT count (*)
FROM database.USAGE
WHERE SERVICE_TYPE = 'C'
AND ACCOUNT = 4837
,       a_sum =
( SELECT sum (minutes)
FROM database.USAGE
WHERE SERVICE_TYPE = 'DA'
AND ACCOUNT = 4837
WHERE   account = 4837;By the way, why are you using double-quotes around 4837? If it's a string, enclose it in single quotes. If it's a number (which I'm assuming in my code), don't enclose it in anything.
WARNING: scalar sub-queries are somewhat like duct tape: they're extremely useful in certain places, and those places account for about 1% of their use. The other 99% of the time, there's a better way to do things, though the better way may require more expertise.