計數數據

Question

我有表：

========================================================== 
|id | before | after | freq | id_sentence | document_id | 
========================================================== 
| 1 | a | b | 1 |  0  |  1  | 
| 2 | c | d | 1 |  1  |  1  | 
| 3 | e | f | 1 |  1  |  1  | 
| 4 | g | h | 2 |  0  |  2  | 
========================================================== 

我想要得到的數據的數量取決於id_sentence和freq所以結果必須是1 2 1 下面的代碼：

$query = mysql_query("SELECT freq FROM tb where document_id='$doc_id' "); 
    while ($row = mysql_fetch_array($query)) { 
     $stem_freq = $row['freq']; 
     $total = $total+$stem_freq; 

但結果仍然是錯誤的。請幫我..謝謝:)

Answer 1

如果我理解你的問題，你想在計算freq爲每個不同的id_sentence總和爲特定document_id。

嘗試以下SQL：

SELECT id_sentence, SUM(freq) as freq FROM tb WHERE document_id = 1 GROUP BY(id_sentence) 

結果將是與id_sentence數據的行和相應的總freq。之後不需要手動總結事情。

看到這個SQL小提琴：http://sqlfiddle.com/#!2/691ed/8

Answer 2

我想你可以做這樣的事情

SELECT count(*) AS count FROM tb GROUP BY(id_sentence,freq) 

做你想要的票。你甚至可以做類似

SELECT count(*) AS count, id_sentence, freq FROM tb GROUP BY(id_sentence,freq) 

知道哪個id_sentence，freq組合的計數是。