从不同的行中选择不同的值

Question

<?php
include("includes/dbconnect.php");
$getTagsQuery = mysql_query("
select tag, sum(tagCount as tagCount) from
(select tag1 as tag, count(*) as tagCount from videos GROUP BY tag1
UNION
select tag2 as tag, count(*) as tagCount from videos GROUP BY tag2
UNION
select tag3 as tag, count(*) as tagCount from videos GROUP BY tag3
UNION
select tag4 as tag, count(*) as tagCount from videos GROUP BY tag4
UNION
select tag5 as tag, count(*) as tagCount from videos GROUP BY tag5)
GROUP BY tag
");
while ($row = mysql_fetch_array($getTagsQuery)){
echo "
    ".$row['tagCount']."
    ";
}
?>

Hello, I have this code. What i need to do is to get the number of times that a different tag appears in the mentioned rows. Without repeating Tags. Why is it not working? Can somebody help? I am failing to get it to work.

Ty

Answer 1

if you want sum the numbers of all tags you should remove the last group by, to be:

$getTagsQuery = mysql_query("
select tag, sum(tagCount as tagCount) from
(select tag1 as tag, count(*) as tagCount from videos GROUP BY tag1
UNION
select tag2 as tag, count(*) as tagCount from videos GROUP BY tag2
UNION
select tag3 as tag, count(*) as tagCount from videos GROUP BY tag3
UNION
select tag4 as tag, count(*) as tagCount from videos GROUP BY tag4
UNION
select tag5 as tag, count(*) as tagCount from videos GROUP BY tag5)
");

Answer 2

首先，您的查询看起来有些怪异，但由于SUM()函数sum(tagCount as tagCount) ，实际上可能是

select tag, sum(tagCount) as tagCount from

Answer 3

Your specific syntax problems are the typo in the outer select and the lack of alias on the subquery.

This is the correct query:

select tag, sum(tagCount) as tagCount
from ((select tag1 as tag, count(*) as tagCount from videos GROUP BY tag1
      ) UNION ALL
      (select tag2 as tag, count(*) as tagCount from videos GROUP BY tag2
      ) UNION ALL
      (select tag3 as tag, count(*) as tagCount from videos GROUP BY tag3
      ) UNION ALL
      (select tag4 as tag, count(*) as tagCount from videos GROUP BY tag4
      ) UNION ALL
      (select tag5 as tag, count(*) as tagCount from videos GROUP BY tag5
      )
     ) t
GROUP BY tag;

The three key changes:

• Fixing the outer select clause.
• Using UNION ALL instead of UNION .
• Adding an alias for the subquery.