SQL.usingAggregateFuncInSelectList

8/10/2019 SQL.usingAggregateFuncInSelectList

http://slidepdf.com/reader/full/sqlusingaggregatefuncinselectlist 1/3

Accessing and Changing Relational Data (SQL Server 2000)

Using Aggregate Functions in the Select ListAggregate functions (such as SUM, A!, C"U#$, C"U#$(%), MA&, and M'#) generate suar values in

*uer result sets+ An aggregate function (ith the e-ce.tion of C"U#$(%)) .rocesses all the selected

values in a single colun to .roduce a single result value+ Aggregate functions can /e a..lied to all ros

in a ta/le, to a su/set of the ta/le s.ecified / a 1R clause, or to one or ore grou.s of ros in the

ta/le+ hen an aggregate function is a..lied, a single value is generated fro each set of ros+

$his e-a.le calculates the su of ear3to3date sales for all /oo4s in the titles ta/le5

USE pubs

SELECT SUM(ytd_sales)

FROM titles

1ere is the result set5

------------------

97446

(1 !"(s) a##e$ted)

ith this *uer, ou can find the average .rice of all /oo4s if .rices ere dou/led5

USE pubs

SELECT a%&(pi$e ' )

FROM titles


------------------

9*+

(1 !"(s) a##e$ted)

$he ta/le shos the snta- of the aggregate functions and their results (expression is alost alas a

colun nae)+

Aggregate function Result

SUM(6ALL 7 D'S$'#C$8 expression) $otal of the values in the nueric e-.ression

A!(6ALL 7 D'S$'#C$8 expression) Average of the values in the nuerice-.ression

C"U#$(6ALL 7 D'S$'#C$8 expression) #u/er of values in the e-.ression

C"U#$(*) #u/er of selected ros

MA&(expression) 1ighest value in the e-.ression

M'#(expression) Loest value in the e-.ression

SUM, A!, C"U#$, MA&, and M'# ignore null values9 C"U#$(%) does not+

$he o.tional 4eord D'S$'#C$ can /e used ith SUM, A!, and C"U#$ to eliinate du.licate values

/efore an aggregate function is a..lied (the default is ALL)+

SUM and A! can /e used onl ith nueric coluns, for e-a.le int, smallint, tinyint, decimal,

numeric, float, real, money, and smallmoney data t.es+ M'# and MA& cannot /e used ith bit data

t.es+ Aggregate functions other than C"U#$(%) cannot /e used ith text and image data t.es+



ith these e-ce.tions, aggregate functions can /e used ith an t.e of colun+ :or e-a.le, in a

character data t.e colun, use M'# (iniu) to find the loest value (the one closest to the

/eginning of the al.ha/et)5

USE pubs

SELECT M,(au_l.a/e)

FROM aut0!s


------------------

e..et

(1 !"(s) a##e$ted)

$he result t.e returned / an aggregate function a have a larger .recision than the in.uts so that

the result t.e is large enough to hold the aggregated result value+ :or e-a.le, the SUM or A!

functions return an int value hen the data t.e of the in.uts is smallint or tinyint+ :or ore

inforation a/out the data t.e returned / an aggregate function, see the to.ic for the function in

Microsoft; SQL Server< 2000 $ransact3SQL Reference+

Note $he out.ut for stateents, involving M'# or MA& on character coluns, de.ends on the collation

chosen during installation+ :or ore inforation a/out the effects of different collations, see SQL Server

Collation :undaentals+

hen aggregate functions are used in a select list, the select list can contain onl5

• Aggregate functions+

• !rou.ing coluns fro a !R"U= >? clause+

• An e-.ression that returns the sae value for ever ro in the result set, such as a constant+

:or ore inforation a/out generating aggregate values for result sets containing ulti.le ros, see

!rou.ing Ros ith !R"U= >?+

Aggregate functions cannot /e used in a 1R clause+ 1oever, a SLC$ stateent ith aggregate

functions in its select list often includes a 1R clause that restricts the ros to hich the aggregate

function is a..lied+ 'f a SLC$ stateent includes a 1R clause (/ut not a !R"U= >? clause), an

aggregate function .roduces a single value for the su/set of ros s.ecified / the 1R clause+ $his is

true hether it is o.erating on all ros in a ta/le or on a su/set of ros defined / a 1R clause+

Such a function is called a scalar aggregate+

$his *uer returns the average advance and the su of ear3to3date sales for /usiness /oo4s onl5

USE pubs

SELECT 23(ad%a.$e)5 SUM(ytd_sales)

FROM titles

ERE type 8 busi.ess


--------- -------

65:1* +;7::

http://msdn.microsoft.com/en-us/library/aa174903(SQL.80).aspx










(1 !"(s) a##e$ted)

?ou can use ore than one aggregate function in the sae select list and .roduce ore than one scalar

aggregate in a single SLC$ stateent+

See Also

Aggregate :unctions

SLC$





Documents

SQL.usingAggregateFuncInSelectList