analytical sql functions 1

8/14/2019 Analytical SQL Functions 1

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Analytical SQL Functions theory and examples Part 2

on the Order By andWindowing lauses

To understand how Analytical Functions are used in SQL statements, you really have to look

at the four different parts of an Analytical clause:

the analytical !unction, for eample A!", L#A$, %#&'#(T)L#*&A(+

the partitioning clause, for eample %A&T)T)( -. /o0 or %A&T)T)( -. dept, /o0

the order "y clause, for eample order 0y /o0 nulls last

the windowing clause, for eample &A("# 1(-1($#$ %'#$)(" or &2S1(-1($#$ FLL2)("

(ote that typically only the Analytical Function is re3uired and the other clauses are

optional4 5owever, for certain functions, an rder -y clause may 0e re3uired4

This post will focus on the rder -y and 2indowin6 'lauses4 %art 7 of this seriesAnalytical

SQL Functions 8 theory and eamples 8 %art 7 on the %artition 'lausediscussed the %artition

'lause and the over9all structure of Analytical #pressions4

rder -y 'lause.ou may wonder what role an &$#& -. clause can play in an Analytical Function4 2e will

investi6ate4

There are some Analytical Functions that return information a0out the relative position of a

record &2*(1;-#&, &A(+, $#(S#*&A(+


2/14

from emp

order

by deptno

, sal desc

, comm desc

, hiredate desc

&esults:

ENAME DE!N" #A$ %&'EDA!E #A$_'AN_&N_DE! #A$_'AN_"E'A$$

***********************************************************************

+$A' - ./0--1*23N*4 5

M&$$E' - 6--.6*2AN*4. . 1

&N7 .- 0---4*N"*4

#+"!! .- 6---1*A'*48 . .

9"'D .- 6----6*DE+*4 6 6

2"NE# .- .180-.*A'*4 / /

ADAM# .- --.6*MA:*48 0 .

#M&!% .- 4--8*DE+*4- 5 /

;$AE 6- .40--*MA:*4 0

A$$EN 6- 5--.-*9E;*4 . 8

!3'NE' 6- 0---4*#E*4 6 4

MA'!&N 6- .0-.4*#E*4 /


3/14

To make row*num0er< meanin6ful, you must specify within what orderin6 you want to have

the row*num0er


4/14

The order 0y clause as used within Analytical #pressions is no different from the rder -y

used at the end of Select statements4 rder -y can make use of multiple columns, make use

of functions 8 /ust not analytical functions= 8 , 0e in AS'#($)(" or $#S'#($)(" order and

either put (1LL values first (1LLS F)&ST< or last (1LLS LAST(sal)over (partition by=ob))

)sal_rank_in_dept

from emp

order

by deptno

, sal desc

5owever, the net 3uery solves the issue and 6ives us the answer we were lookin6 for4

A6ain, a useful trick: if we need analytical results within an Analytical Function, we use an in9

line view to produce those results and enrich the records we process in the outer Analytical

Function with those results4

selectename

, deptno

, =ob

, sal

, av>_sal_in_=ob av>_=ob_sal

, sal *av>_sal_in_=ob sal_min_=ob_av>

, row_number()over (partition bydeptno

order by(sal *av>_sal_in_=ob)

)sal_min_=ob_av>_rank_in_dept

from (selectename

, deptno

, =ob

, sal

, av>(sal)over (partition by=ob)av>_sal_in_=ob

from emp

)


5/14

order

by deptno

, sal desc

&esults:

ENAME DE!N" 2"; #A$ A7_2";_#A$ #A$_M&N_2";_A7

#A$_M&N_2";_A7_'AN_&N_DE!

*****************************************************************

****************************

+$A' -MA'E!EE' ./0- ./0- -

M&$$E' -+$E' 6-- -68?0 .5.?0

.

&N7 .-'E#&DEN! 0--- 0--- -

/

#+"!! .-ANA$:#! 6--- 6--- -.

9"'D .-ANA$:#! 6--- 6--- -

6

2"NE# .-MANA7E' .180 .1.?0 5.?0

5

ADAM# .-+$E' -- -68?0 5.?0

0

#M&!% .-+$E' 4-- -68?0 *.68?0

;$AE 6-MANA7E' .40- .1.?0 *5.?0

/

A$$EN 6-#A$E#MAN 5-- /-- .--

5

!3'NE' 6-#A$E#MAN 0-- /-- --

0

MA'!&N 6-#A$E#MAN .0- /-- *0-

o04 )n

that respect is >A;#S, who works as 'L#&+ in the same department as ;A&T)(, is somewhat

0etter off: he comes third in terms of 6ap with the avera6e salary in his /o0 cate6ory4 ) admit

thou6h that this 3uery is 3uite farfetched 8 tryin6 to illustrate all concepts in the contet of


6/14

#;% and $#%T is perhaps overam0itious4

#an$ %s& #ow'(um"er

) always have trou0le fi6urin6 out why ) should &A(+ or $#(S#*&A(+< instead of

&2*(1;-#&4 Also see SQL for $ata 2arehousin6 in the racle 7?6 $ata 2arehousin6

"uide4 &2*(1;-#& seems to 6ive me the result ) am lookin6 for, however &A(+ is

specifically created to answer this type of 3uestion4
http://download-west.oracle.com/docs/cd/B13789_01/server.101/b10736/analysis.htm#i1007779%2311237http://download-west.oracle.com/docs/cd/B13789_01/server.101/b10736/analysis.htm#i1007779%2311237http://download-west.oracle.com/docs/cd/B13789_01/server.101/b10736/analysis.htm#i1007779%2311237http://download-west.oracle.com/docs/cd/B13789_01/server.101/b10736/analysis.htm#i1007779%2311237


7/14

selectename

, hiredate

, sal

, rank()over (partition bydeptno

order bysal desc,comm desc ,hiredate desc

)sal_rank_in_dept

, rank()over (order bysal desc)sal_rank_overall

from emp

order

by sal desc

, comm desc

, hiredate desc

ENAME %&'EDA!E #A$ #A$_'AN_&N_DE! #A$_'AN_"E'A$$

*************************************************************

&N7 4*N"*4 0---

#+"!! 1*A'*48 6--- . .

9"'D -6*DE+*4 6--- 6 .

2"NE# -.*A'*4 .180 / /

;$AE -*MA:*4 .40- 0

+$A' -1*23N*4 ./0- 5

A$$EN .-*9E;*4 5-- . 8

!3'NE' -4*#E*4 0-- 6 4

M&$$E' .6*2AN*4. 6-- . 1

MA'!&N .4*#E*4 .0- / -


8/14

Take for eample this 3uery:

selectename

, =ob

, sal

, av>(sal)over (partition by=ob)=ob_av>

, av>(sal)over ()total_av>

from emp

where sal @.0--

order

by =ob

ENAME 2"; #A$ 2";_A7 !"!A$_A7

*************************************************

#M&!% +$E' 4-- -68?0600?00005

ADAM# +$E' -- -68?0600?00005

2AME# +$E' 10- -68?0600?00005

M&$$E' +$E' 6-- -68?0600?00005

+$A' MA'E!EE' ./0- ./0-600?00005

A$$EN #A$E#MAN 5-- /--600?00005

!3'NE' #A$E#MAN 0-- /--600?00005

o0 as the current row4 For S;)T5 the >-*A!" value was calculated as the Avera6e Salary

for all #mployees returned 0y the 3uery i4e4 with a salary @ B??< in the same >o0 as S;)T5

i4e4 'lerks(sal)over (partition by=ob

order by hiredate

)=ob_av>

from emp

where sal @.0--

order

by =ob


9/14

, hiredate

we 6et a result that may surprise you:

ENAME 2"; #A$ %&'EDA!E 2";_A7

************************************************

#M&!% +$E' 4--8*DE+*4- 4--

2AME# +$E' 10--6*DE+*4 480

M&$$E' +$E' 6--.6*2AN*4.-5?55558

ADAM# +$E' --.6*MA:*48 -68?0

+$A' MA'E!EE' ./0--1*23N*4 ./0-

A$$EN #A$E#MAN 5--.-*9E;*4 5--

-*A!" is no lon6er constant within a partition4 5ere is the

eplanation: 0y specifyin6 the order 0y clause, we in fact told the SQL en6ine two thin6s

74 order the rows within the >-9partitions on hiredate so the first hired employee in a

/o0 is listed first in the partition-*A!" value found for S;)T5 9 the first hired 'L#&+ 9 is arrived

at in the followin6 way: take all #mployees returned 0y the 3uery and from that set the

partition of all 'L#&+S4 rder them 0y hiredate4 (ow startin6 from the current record 9

S;)T5 9 take his Salary and the Salary9values of all precedin6 rows4 Since there are no

precedin6 rows in the partition, S;)T5Cs salary is the only one used for calculatin6 the

avera6e and is therefore e3ual to the avera6e4


11/14

>-*A!" for Turner 9 the third hired employee in the 6roup of SAL#S;#( 9 is calculated

usin6 the Salaries of T1&(#& himself and his two previously hired collea6ues 9 ALL#( and

2A&$4 The last SAL#S;A(, ;A&T)(, is outside the window4

)t follows from the a0ove that only for the last hired employees in each partition 9 the ones

where the window overlaps with the entire partition 9 the >-*A!" is e3ual to salary of all

employees with the same /o0 as found in the previous 3uery


12/14

The net ima6e compares the runnin6 avera6e with an order 0y 9 and therefore implicit

windowin6 clause< with the avera6e calculated with the same partition clause 0ut without


13/14

order 0y:

The reverse of the a0ove 3uery is the followin6, where the >-*A!" is calculated over the

current employee and all later hired collea6ues in the same >o0:

selectename

, =ob


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, sal

, hiredate

, av>(sal)over (partition by=ob

order by hiredate

ran>e between current row andunbounded followin>

)=ob_av>

from emp

where sal @.0--

order

by =ob

ENAME 2"; #A$ %&'EDA!E 2";_A7

************************************************

#M&!% +$E' 4--8*DE+*4- -68?0

2AME# +$E' 10--6*DE+*45?55558

M&$$E' +$E' 6--.6*2AN*4. .--

ADAM# +$E' --.6*MA:*48 --

+$A' MA'E!EE' ./0--1*23N*4 ./0-

A$$EN #A$E#MAN 5--.-*9E;*4 /--

analytical sql functions 1

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