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www.mainframes-online-training.weebly.com Polsani Anil Kumar
DB2 SQL Select
DB2 Training class 08
http://www.mainframes-online-training.weebly.com/http://www.mainframes-online-training.weebly.com/http://www.mainframes-online-training.weebly.com/
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A Closer Look at the SELECTStatement
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Seven Diferent Clauses
These clauses are processed in the order shown
1. The DISTI!T clause
". The #$%& clause' Identifies the Table ame
(. The )*+$+ clause
,. The $%P /0 clause
. The *A2I clause3. The %$D+$ /0 clause
4. The #+T!* #I$ST clause
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DISTICT
Suppose you wanted to retrie5e e5ery uni6ue 5alue 7no
duplicates8 for
a column in a table
S+9+!T DISTI!T :ob #$%& employee
If you wanted to change the name of the column in the result
data set
produced. 0ou could do so by e;ecuting a S+9+!T statement
that
loo
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The !"E#E Clause
The )*+$+ clause is used to tell the D/" Database &anager
how to
select the rows based on a condition.
Si; common types of )*+$+ clause
$elationalPredicates' , =, =,
/+T)++' BETWEEN 60000.00 AND 70000.00
9IK+' LIKE S_ and 'S%'
I' IN (W01,W02
+=ISTS
IS99
+ach of these predicates can be used alone> or they can be
combined
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!"#$ B& a)*+ -AIN! a)*+
!"#$ B& a)*+
The $%P /0 clause is used to tell the D/" Database &anager
how
to organi?e rows of data returned in the result data set
produced in
response to a 6uery.
+=' S+9+!T )$KD+PT>&A=7+SA98 #$%& +&PTA/9+
$%P
/0 )$KD+PT@
T/+ -AIN! a)*+
The *A2I clause is used to apply further selection criteria
tocolumns referenced in a $%P /0 clause. This clause beha5es li
e;cept that it refers to data that has already been
grouped
+;' S+9+!T )$KD+PT>&A=7+SA98 #$%& +&PTA/9+ $%P
/0
)$KD+PT *A2I &A=7+SA98 3BBB@
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#"DE" B& a)*+
The %$D+$/0clause is used to tell the D/" Database &anager
how
to sort and order the rows that are to be returned in a result
data set
If the ascending order is
used> and if the descending
order is used.
+;1' S+9+!T +&P%>+A&+>+SA9 #$%&
+&PTA/9+
%$D+$ /0 +&P%@+;"' S+9+!T +&P%>+A&+>+SA9
#$%& +&PTA/9+
%$D+$ /0 +A&+>+SA9 D+S!@
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$ETC" $I#ST Clause
The #+T!*#I$STclause is used to limit the number of rows
returned
to the result data set produced in response to a 6uery.
)hen used> the #+T!* #I$ST clause is followed by a positi5e
integer
5alue and the words $%)S %90.
+;'
S+9+!T +&P%>+A&+>)$KD+PT #$%& +&PTA/9+
#+T!*
#I$ST " $%)S %90@
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Built I $unction
A built-in functionis a function that is supplied with D/" D/.
The
result of a function is a single 5alue deri5ed by applying the
operation
of the function to the arguments.
S&
&A=
&I
A2
!%T78E !%T7DISTI!T !%98
9+T*
!%!AT
S/ST$
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C%&T $unction
The !%T function returns the number of rows or 5alues in a set
of
rows or 5alues. The argument of !%T78 is a set of rows.
SELET #$NT( "#3 E3TAB4
The argument of !%T7DISTI!T expression8 is a set of 5alues.
Thefunction is applied to the set of 5alues deri5ed from the
argument 5alues
by the elimination of null 5alues and duplicate 5alues.
SELET #$NT(ESAL "#3 E3TAB4
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'A( 'I ) S&'
The &A=E&I column function returns the ma;imum 5alue in
a set of
5alues in a group. The function is applied to the set of 5alues
deri5ed from
the argument 5alues by the elimination of null 5alues.
The specification of DISTI!T has no effect on the result and is
not
ad5ised.
SELET 3A53IN(ESAL AS 3A5_SAL "#3 E3TAB4
The S& function returns the sum of a set of numbers. The
function is
applied to the set of 5alues deri5ed from the argument 5alues by
the
elimination of null 5alues. If DISTI!T is specified>
duplicate 5alues areeliminated.
The result can be null. If the function is applied to the empty
set> the result
is a null 5alue. %therwise> the result is the sum of the
5alues in the set.
SELET S$3(ESAL AS ESAL "#3 E3TAB4
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A*+ $unction
The A2 function returns the a5erage of a set of numbers. The
argument 5alues must be any built-in numeric data type and their
sum
must be within the range of the data type of the result.
The result can be null. If set of 5alues is empty>
%therwise> the result
is the a5erage 5alue of the set.
A2 disregards any 99S in any column in5ol5ed
SELET A!(ESAL AS ESAL "#3 E3TAB4
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C%CAT S&BST# ) LE+T"
The !%!AT function combines two arguments. The result of the
function is a string that consists of the first argument string
followed
by the second.
SELET #NAT(I"STN3E, LASTNA3E "#3 E3L#&EE
The S/ST$ and S/ST$I functions return a substring of a
string.
SELET S$BST"(ENA3E, ,8 "#3 E3L#&EE4
The 9+T* function returns the length of a 5alue
SELET LEN!T-(EADD" "#3 E3L#&EE4
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Kumar
Thank ,ou
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