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Is there adjacent row operation?

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Is there adjacent row operation? General SQL help. Help with MySQL, MSSQL, Oracle, mSQL, PostgreSQL, etc.

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  #1  
Old August 8th, 2002, 03:20 PM
lambda lambda is offline
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Is there adjacent row operation?
I Need help. Problem is like this:

BASE TABLE (say the historical price of product X)

Year Price
---- ------
1960 5
1962 7
1967 15
1970 20
1980 30
1986 44
1992 50
2000 60


QUERY RESULT (with filter say Year Between 1967 And 1986)

Year1 Year2 Price1 Price2 PriceInc
----- ----- ------ ------- --------
1967 1970 15 20 5
1970 1980 20 30 10
1980 1986 30 44 14

the last column is a calculated field (Price2-Price1).

can this query be produced by SQL statement?
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  #2  
Old August 9th, 2002, 02:12 AM
sager sager is offline
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RE: Is there adjacent row operation?
I'm not sure if it will work, but I think it might:

select Year1, Year2, Price1, Price2, (Price2 - Price1) as PriceInc ....

Not sure though, never tried it, but it's worth a shot;)
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Old August 9th, 2002, 12:38 PM
lambda lambda is offline
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RE: Is there adjacent row operation?
thanks, ShaneO and sager, for your response. i really appreciated your time spent on this.

However i must note that the peculiarity of this problem is the fact that the query result is always consecutive rows. And note that for a given row, the first column value (Year1) is always the same as the second column value (Year2) of the PRECEDING row. This is also true for the Price columns.

I really need help on this one. Thanks.

lambda
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  #4  
Old August 9th, 2002, 01:19 PM
EvilivE EvilivE is offline
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RE: Is there adjacent row operation?
Here is a hack:
php Code:
Original - php Code 
  1. <?
  2. $query1 = "select year, price from table_name where year>=1967 and year<1986 order by year asc";
  3. $result1 = mysql_query($query1);
  4. while($row1 = mysql_fetch_array($result1)){
  5.   if($row1['year'] != '1986'){
  6.     $query2 = "select year, price from table_name where year>".$row1['year']."order by year asc limit 1";
  7.     $result2 = mysql_query($query2);
  8.     $row2 = mysql_fetch_array($result2);
  9.   }
  10.   echo $row1['year']." ".$row2['year']." ".$row1['price']." ".$row2['price']." ".($row2['price'] - $row1['price'])."<br>";
  11. }
  12. ?>
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  #5  
Old August 9th, 2002, 01:22 PM
EvilivE EvilivE is offline
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RE: Is there adjacent row operation?
The 2nd year comparison in $query1 should be <=
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  #6  
Old August 9th, 2002, 01:43 PM
EvilivE EvilivE is offline
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RE: Is there adjacent row operation?
hang-on ... wait a minute ... stop.
Sorry 'bout that but the mountain dew is wearing off and its past my bedtime. This is it:
php Code:
Original - php Code 
  1. <?
  2. $query1 = "select year, price from table_name where year>=1967 and year<1986 order by year asc";
  3. $result1 = mysql_query($query1);
  4. while($row1 = mysql_fetch_array($result1)){
  5.   $query2 = "select year, price from table_name where year>".$row1['year']."order by year asc limit 1";
  6.   $result2 = mysql_query($query2);
  7.   $row2 = mysql_fetch_array($result2);
  8.  
  9.   echo $row1['year']." ".$row2['year']." ".$row1['price']." ".$row2['price']." ".($row2['price'] - $row1['price'])."<br>";
  10. }
  11. ?>
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