MYSQL全文 - 意外的結果

Question

我有一個80,000行的數據庫，當我測試了一些FULLTEXT查詢時，我遇到了意想不到的結果。我從MYSQL刪除停用詞，並已設置的最小字長爲3

當我做這個查詢：

SELECT `sentence`, MATCH (`sentence`) AGAINST ('CAN YOU FLY') AS `relevance` 
FROM `sentences` 
WHERE MATCH (`sentence`) AGAINST ('CAN YOU FLY') 
ORDER BY `relevance` DESC 

它給出了這樣的結果：

NO A FLY WITHOUT WINGS WOULD BE CALLED A WINGLESS | 10.623517036438 
I CAN FLY           | 7.61278629302979 
I CAN FLY :)          | 7.61278629302979 
CAN YOU FLY?          | 7.61278629302979 
THEY CAN FLY          | 7.61278629302979 
YOU AM NOT FLY         | 7.61278629302979 
CAN YOU FLY          | 7.61278629302979 
HAVE YOU EVER SWALLOWED A FLY?     | 7.52720737457275 
I JUST WANNA FLY         | 7.52720737457275 

爲什麼「沒有A沒有翅膀的飛行將被稱爲無翼「獲得了最高的相關性，它只包含其中一個單詞......另外，」CAN YOU FLY「如何出現在頂部，這完全匹配。

我想用大多數匹配的關鍵詞排序，然後按大多數順序排列，然後用最少的單詞排序。這將使邏輯結果：

CAN YOU FLY 
CAN YOU FLY? 
I CAN FLY 
THEY CAN FLY 
I CAN FLY :) 
YOU AM NOT FLY 
HAVE YOU EVER SWALLOWED A FLY? 
I JUST WANNA FLY 
NO A FLY WITHOUT WINGS WOULD BE CALLED A WINGLESS 

Answer 1

用於計算的公式是提供MySQL Internals Manual：

w = (log(dtf)+1)/sumdtf * U/(1+0.0115*U) * log((N-nf)/nf) 

其中

dtf  is the number of times the term appears in the document 
sumdtf is the sum of (log(dtf)+1)'s for all terms in the same document 
U  is the number of Unique terms in the document 
N  is the total number of documents 
nf  is the number of documents that contain the term 

第一個文本顯然有更多的內容比其他人。該公式極大地依賴於U，這是文檔中唯一條款的數量。

通過您的意見，我會建議使用Boolean Fulltext Search：

SELECT `sentence`, MATCH (`sentence`) AGAINST ('CAN YOU FLY' IN BOOLEAN MODE) AS `relevance` 
FROM `sentences` 
WHERE MATCH (`sentence`) AGAINST ('CAN YOU FLY' IN BOOLEAN MODE) 
ORDER BY `relevance` DESC