Aggregate Functions in the SELECT Clause
Aggregate Functions in the SELECT Clause
The following query is an example of a query with multiple expressions in the select clause:
SELECT c.name, c.country.name
FROM customer c
WHERE c.lastname =
'Coss' AND c.firstname = 'Roxane'
It returns a list of Object[] elements where the first array element is a string denoting the
customer name and the second array element is a string denoting the name of the customer's
country.
Aggregate Functions in the SELECT Clause
The result of a query may be the result of an aggregate function, listed in
TABLE 2710
Aggregate Functions in Select Statements
Name
Return Type
Description
AVG
Double
Returns the mean average of the fields.
COUNT
Long
Returns the total number of results.
MAX
the type of the field
Returns the highest value in the result
set.
MIN
the type of the field
Returns the lowest value in the result
set.
SUM
Long
(for integral fields)Double (for floating
point fields)BigInteger (for BigInteger
fields)BigDecimal (for BigDecimal fields)
Returns the sum of all the values in the
result set.
For select method queries with an aggregate function (AVG, COUNT, MAX, MIN, or SUM) in the
SELECT
clause, the following rules apply:
For the AVG, MAX, MIN, and SUM functions, the functions return null if there are no values to
which the function can be applied.
For the COUNT function, if there are no values to which the function can be applied, COUNT
returns 0.
The following example returns the average order quantity:
SELECT AVG(o.quantity)
FROM Order o
The following example returns the total cost of the items ordered by Roxane Coss:
Full Query Language Syntax
The Java EE 5 Tutorial · September 2007
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