为什么我的查询没有定义这个值？

Question

I have a database query that displays a list of national birds. I picked up a script that adds a cool detail: The ability to add asterisks, stars, etc. to birds that represent more than one nation.

However, I must have changed something in my code or database table that broke it. I now get the error message Undefined index: Stars. Can anyone spot the problem?

I pasted the query into phpMyAdmin > SQL, and it seems to work OK, displaying rows representing nations with national birds...

SELECT GS.N, GS.IDArea SymArea, GS.IDSymbol, GS.URL, GS.Title,
GS.PageKind3, GS.Symbol, GS.Latin, GS.Desig, GS.DesigGen, GS.DesigGroup, GS.Date,
GG.N, GG.IDArea, GG.Name, GG.Type, GG.IDParent, GG.IDParent2, GG.Parent, GG.Parent2,    GG.IDReg, 
T.Stars 
FROM gs AS GS 
LEFT JOIN gw_geog AS GG ON GG.IDArea = GS.IDArea 

LEFT JOIN ( 
 SELECT Latin, COUNT(Latin) as Stars 
 FROM gs 
 GROUP BY Latin
) as T ON GS.Latin = T.Latin 

WHERE GS.DesigGen = 'bird' AND GG.Type = 'nat' AND GS.Symbol != '' 
OR GS.DesigGen = 'bird' AND GG.Type = 'dep' AND GS.Symbol != '' 
GROUP BY GS.IDArea ORDER BY GS.N

The most important value is probably GS.Latin, which simply lists various birds' Latin, or scientific names. It appears that the above query isn't "connecting" with the script in my loop, below. Does anyone have a hunch what the problem is?

while ($row = $stm->fetch())
{

  switch (TRUE)
 { 
  case ($row['Stars'] == 2): 
  $star_rating = ' (2)'; 
  break; 
  case ($row['Stars'] == 3): 
  $star_rating = ' (3)'; 
  break; 
  case ($row['Stars'] == 4): 
  $star_rating = ' (4)'; 
  break; 
  case ($row['Stars'] > 5): 
  $star_rating = ' (5 or more)'; 
  break; 
  default: 
  $star_rating = ''; 
  break; 
 }

}

Answer 1

I think your left join make the Stars field to be null try to replace T.Stars in the query fields to

COALESCE(T.Stars,0) AS `Stars`

This will set a default 0 if the field is null