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Tip of the Day
Language: SQL Server
Expertise: Beginner
Sep 14, 1999

Retrieving the Greatest Value from a Group

Question:
I have a table like this one:
 
Day_Period_Money 
(daydate date,
 period  number,
 amount  number);
Here is an example of some data:
 
daydate  period amount
01/01/99    1     10
01/01/99    2     20
01/01/99    3     15
01/02/99    1     30
01/02/99    2     25
01/02/99    3     20
How do I get the largest amount for each day with the period? The result should look like this:
01/01/99    2      20
01/02/99    1      30

Answer:
What you want and what you got are two different things, no? You are trying to generate two different groups and, as I'm sure you found out, if you include type with date in the group by expression, you'll wind up with all the values for the day and all their groups of that day, which is not what you want.

The answer is, you can't solve this in one pass, you need to do it as a two-step query—one to get the largest amount on a day and the other to get the type with its amount.

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