Is there adjacent row operation?

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August 8th, 2002, 04:20 PM

lambda

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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?

August 9th, 2002, 03:12 AM

sager

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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;)

August 9th, 2002, 01:38 PM

lambda

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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

August 9th, 2002, 02:19 PM

EvilivE

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RE: Is there adjacent row operation?

Here is a hack:

php Code:

Original - php Code

<?
$query1 = "select year, price from table_name where year>=1967 and year<1986 order by year asc";
$result1 = mysql_query($query1);
while($row1 = mysql_fetch_array($result1)){
  if($row1['year'] != '1986'){
    $query2 = "select year, price from table_name where year>".$row1['year']."order by year asc limit 1";
    $result2 = mysql_query($query2);
    $row2 = mysql_fetch_array($result2);
  }
  echo $row1['year']." ".$row2['year']." ".$row1['price']." ".$row2['price']." ".($row2['price'] - $row1['price'])."<br>";
}
?>

August 9th, 2002, 02:22 PM

EvilivE

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Location: Milwaukee, WI USA

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RE: Is there adjacent row operation?

The 2nd year comparison in $query1 should be <=

August 9th, 2002, 02:43 PM

EvilivE

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Location: Milwaukee, WI USA

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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

<?
$query1 = "select year, price from table_name where year>=1967 and year<1986 order by year asc";
$result1 = mysql_query($query1);
while($row1 = mysql_fetch_array($result1)){
  $query2 = "select year, price from table_name where year>".$row1['year']."order by year asc limit 1";
  $result2 = mysql_query($query2);
  $row2 = mysql_fetch_array($result2);
 
  echo $row1['year']." ".$row2['year']." ".$row1['price']." ".$row2['price']." ".($row2['price'] - $row1['price'])."<br>";
}
?>

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