Adobe 38043740 - ColdFusion Standard - Mac Development Manual page 448

DEVELOPING COLDFUSION 9 APPLICATIONS
Accessing and Using Data
Using aggregate functions
Aggregate functions operate on a set of data and return a single value. Use these functions for retrieving summary
information from a table, as opposed to retrieving an entire table and then operating on the recordset of the entire
table.
Consider using aggregate functions to perform the following operations:
• To display the average of a column
• To count the number of rows for a column
• To find the earliest date in a column
Since not every relational database management system (RDBMS) supports all aggregate functions, refer to the
documentation of your database. The following table lists the aggregate functions that Query of Queries supports:
Function Description
AVG() Returns the average (mean) for a column.
COUNT() Returns the number of rows in a column.
MAX() Returns the largest value of a column.
MIN() Returns the lowest value of a column.
SUM() Returns the sum of values of a column.
Syntax
aggregate_func ::= <COUNT>(* | column_name) | AVG | SUM | MIN | MAX)
([ALL | DISTINCT] numeric_exp)
Example
The following example uses the
SELECT dog_name, AVG(dog_IQ) AS avg_IQ
FROM Dogs
WHERE breed LIKE '%Terrier';
Arbitrary expressions in aggregate functions
Query of Queries supports aggregate functions of any arbitrary expression, as follows:
SELECT lorange, count(lorange+hirange)
FROM roysched
GROUP BY lorange;
Aggregate functions in arbitrary expressions
Query of Queries supports mathematical expressions that include aggregate functions, as follows:
SELECT MIN(lorange) + MAX(hirange)
FROM roysched
GROUP BY lorange;
Using group by and having expressions
Query of Queries supports the use of any arbitrary arithmetic expression, as long as it is referenced by an alias.
function to retrieve the average IQ of all terriers:
AVG()
Last updated 1/20/2012
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