You can use a WHERE clause in a query containing a GROUP BY clause. Rows that don't satisfy the conditions in the WHERE clause are eliminated before any grouping is done. Here's an example:
SELECT type, AVG(price) |
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FROM titles |
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WHERE advance > $5000 |
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GROUP BY type |
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type |
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------------ |
------- |
|
business |
11.96 |
|
mod_cook |
2.99 |
|
popular_comp |
21.48 |
|
psychology |
24.80 |
|
trad_cook |
17.97 |
|
(5 row(s) affected) |
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Only rows with advances greater than $5000 are included in the groups shown in the query results.