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what's the meaning of ampersand in select case statement

Posted on 2011-09-29
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Last Modified: 2012-05-12
select name,
       case sysstat2 & 57344
            when 32768 then "datarows"

What's the meaning of the ampersand in front of '57344'

Thanks in advance
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Question by:gamjaradio
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9 Comments
 
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by:
Pratima Pharande earned 504 total points
ID: 36813581
<% dim iRow
select name,
       case sysstat2 & 57344
            when 32768 then "datarows"

Meaning of this

sysstat2 & 57344   , one of this value either field value of sysstat2 or 57344  is equal to 32768  then "datarows"

in other words condition looks like this

if (sysstat2 = 32768) Or (57344 = 32768 ) then "datarows"
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LVL 143

Assisted Solution

by:Guy Hengel [angelIII / a3]
Guy Hengel [angelIII / a3] earned 500 total points
ID: 36813594
actually,
 case sysstat2 & 57344

is doing a bitwise AND of the 2 values (aka the variable sysstat2 and 57344).
this value will then be compared to the value 32768 , if that matches ....

hope this helps
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Author Comment

by:gamjaradio
ID: 36813625
so, you say....

it compare (sysstat2 == 32768) OR (57344 == 32768) ??
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LVL 39

Assisted Solution

by:Pratima Pharande
Pratima Pharande earned 504 total points
ID: 36813649
yes
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LVL 143

Assisted Solution

by:Guy Hengel [angelIII / a3]
Guy Hengel [angelIII / a3] earned 500 total points
ID: 36813671
as posted above, I have to disagree ...
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LVL 2

Assisted Solution

by:maneksh
maneksh earned 744 total points
ID: 36814235
Hi,

I am afraid Pratima is wrong.

& is a bitwise operator. it converts the operands into binary and evaluates column by column.

Please follow the link to see details

http://manuals.sybase.com/onlinebooks/group-as/asg1250e/sqlug/@Generic__BookTextView/1719;pt=945

Maneksh

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LVL 2

Assisted Solution

by:maneksh
maneksh earned 744 total points
ID: 36814350
Here in your example 57344 is 1110000000000000
and 32768 is 1000000000000000

some examples of  Values of  sysstat2  that could satisfy the condition are
40959  and  32768

Hope this helps

Maneksh
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LVL 2

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by:maneksh
maneksh earned 744 total points
ID: 36814459
Hi,

Looking at your query I think you are looking for the lock scheme of a table  which is maitained in sysstat2 table in bit representation.Bit corresponding to 8192 , 16384 and 32768 represents the lock schema and 57344 is the sum of these 3.


Hope I dint confuse

maneksh


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Assisted Solution

by:Lowfatspread
Lowfatspread earned 252 total points
ID: 36816459
its a bitwise operator signifying a logical and operation is performed on the bit patterns of the two expressions

from

msdn
The bitwise & operator performs a bitwise logical AND between the two expressions, taking each corresponding bit for both expressions. The bits in the result are set to 1 if and only if both bits (for the current bit being resolved) in the input expressions have a value of 1; otherwise, the bit in the result is set to 0.

so basically when dealing with flags/indicators stored as a pattern of bits and you wish to test for some specific values
you calculate the numeric value of the combination that you are interested in and have that logically anded with the total option value...

you can then easier test the result to see if the desired set of conditions is present.
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