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I need to update every twentieth row.

Posted on 2011-03-09
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Last Modified: 2012-05-11
I need to update every twentieth row.

Is there a way in which I can do this without cursors?
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Question by:Mr_Shaw
  • 2
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7 Comments
 
LVL 142

Assisted Solution

by:Guy Hengel [angelIII / a3]
Guy Hengel [angelIII / a3] earned 300 total points
ID: 35084427
you need some "order by" to specify which row is the 20th ...
;with data as (
  select t.*, row_number() over (order by somekeycol) rn
    from yourtable t
)
UPDATE data
    SET x = abc
  WHERE rn % 20 = 0 

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LVL 15

Accepted Solution

by:
derekkromm earned 100 total points
ID: 35084435
update t
set ?=?
from table t
inner join (select PK, row_number() over (order by PK) as 'rownum' from table) t1
on t.PK = t1.PK
where (t1.rownum-1) % 20 = 0
0
 
LVL 51

Expert Comment

by:HainKurt
ID: 35084562
or this:

update t
set myCol=@value
from table t
inner join (
  select PK from (
    select PK, row_number() over (order by PK) as rn from table
  ) x where rn % 20 =0
) t1
on t.PK = t1.PK
0
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Author Comment

by:Mr_Shaw
ID: 35084630
angelIII:

Hi Would, this be a random 1 in 20 or last 20% of rows?
0
 
LVL 51

Assisted Solution

by:HainKurt
HainKurt earned 100 total points
ID: 35084908
try:

update t
set myCol=@value
from table t
inner join (
  select PK from (
    select PK, row_number() over (order by newid()) as rn from mytable
  ) x where rn % 20 =0
) t1
on t.PK = t1.PK
0
 
LVL 142

Expert Comment

by:Guy Hengel [angelIII / a3]
ID: 35084923
% is the modulo operator, nothing about random or last 20 rows ...
http://msdn.microsoft.com/en-us/library/aa276866%28v=sql.80%29.aspx
0
 

Author Closing Comment

by:Mr_Shaw
ID: 35085255
thanks
0

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