SQL語句返回只有兩行

Question

我拿着號的四個不同領域的行的表：人，雜物，里程和包裝袋。由於目前還沒有數據，所有這些字段對於每一行都是0。這些行還有兩個重要的字段，稱爲「縣」，其價值是紐約州的一個縣，「水下」只是1/0（是/否）字段。因此，他們是這個樣子......

County  Underwater People Debris Miles Bags 
Richmond    0  0  0  0 0 
Rockland    1  0  0  0 0 
Nassau    0  0  0  0 0 
Queens    1  0  0  0 0 
Niagara    0  0  0  0 0 

爲了將所有的這一起PHP頁面，我使用很長的SQL語句，有很多工會和縣基本上分離的結果紐約市，長島和紐約州北部，以及其他兩個關於水下和水下的問題，然後是總數。我認爲一次使用的長語句比六次單獨查詢對同一個表更有效，並且會爲我節省一些代碼行。我在所有數據爲0之前使用測試編號，並且它工作正常。現在所有的數據都是0，結果集是全0的一行，然後是一行NULL，沒有別的。由於我使用foreach PHP循環來解析數據，因此我的算法很難實現。我也注意到，如果我即使只將1行數據（即使只有1個字段）更改爲非零值，我也會在結果集中得到另一行。

任何人都可以解釋這種現象和解決辦法或許可供選擇？如果需要，我可以更深入。

這是順便說一下有問題的聲明。備用牆...

SELECT SUM(people) AS people, SUM(debris) AS debris, SUM(miles) AS miles, SUM(bags) AS bags 
FROM `table` 
WHERE county='The Bronx' OR county='Kings' OR county='New York' OR county='Queens' OR county='Richmond' 
UNION 
SELECT SUM(people) AS people, SUM(debris) AS debris, SUM(miles) AS miles, SUM(bags) AS bags 
FROM `table` 
WHERE county='Nassau' OR county='Suffolk' 
UNION 
SELECT SUM(people) AS people, SUM(debris) AS debris, SUM(miles) AS miles, SUM(bags) AS bags 
FROM `table` 
WHERE county='Albany' OR county='Allegany' OR county='Broome' OR county='Cattaraugus' OR county='Cayuga' OR county='Chautauqua' OR county='Chemung' OR county='Chenango' OR county='Clinton' OR county='Columbia' OR county='Cortland' OR county='Delaware' OR county='Dutchess' OR county='Erie' OR county='Essex' OR county='Franklin' OR county='Fulton' OR county='Genesee' OR county='Greene' OR county='Hamilton' OR county='Herkimer' OR county='Jefferson' OR county='Lewis' OR county='Livingston' OR county='Madison' OR county='Monroe' OR county='Montgomery' OR county='Niagara' OR county='Oneida' OR county='Onondaga' OR county='Ontario' OR county='Orange' OR county='Orleans' OR county='Oswego' OR county='Otsego' OR county='Putnam' OR county='Rensselaer' OR county='Rockland' OR county='Saratoga' OR county='Schenectady' OR county='Schoharie' OR county='Schuyler' OR county='Seneca' OR county='Steuben' OR county='StLawrence' OR county='Sullivan' OR county='Tioga' OR county='Tompkins' OR county='Ulster' OR county='Warren' OR county='Washington' OR county='Wayne' OR county='Westchester' OR county='Wyoming' OR county='Yates' 
UNION 
SELECT SUM(people) AS people, SUM(debris) AS debris, SUM(miles) AS miles, SUM(bags) AS bags 
FROM `table` 
WHERE underwater = '0' AND county != '' 
UNION 
SELECT SUM(people) AS people, SUM(debris) AS debris, SUM(miles) AS miles, SUM(bags) AS bags 
FROM `table` 
WHERE underwater = '1' AND county != '' 
UNION 
SELECT SUM(people) AS people, SUM(debris) AS debris, SUM(miles) AS miles, SUM(bags) AS bags 
FROM `table` 
WHERE county != '' AND fname != '' AND lname != '' 

Answer 1

使用UNION ALL而不是UNION。 UNION運算符將在兩個結果集之間丟棄重複行，非常類似於單個結果集的SELECT DISTINCT。 （或者，選擇縣名太，因爲這將導致結果行含有不相同的數據。）

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爲了消除從查詢NULL的行（其是在閒置數據集合函數像SUM()結果套）只是做這樣的事情：

SELECT * FROM (
    your query here 
) AS x 
WHERE x.people IS NOT NULL 

另外，在查詢中改變SUM(x)每次發生於COALESCE(SUM(x), 0)。