全文檢索功能 ON PHP.

而在文章後頭, 只加上了 MySQL FULLTEXT index 相關說明網頁.
===============連結=============
MySQL 4.1 Full-Text Search Functions
MySQL 5.0 Full-Text Search Functions
===============連結=============

在百思不得其解的情況下, 只好順著 MySQL 的相關連結查去.
看著看著, 終於在文章後頭看到了 "解答".
===============節錄=============
For example, although the word 「MySQL」 is present in every row of the articles table shown earlier, a search for the word produces no results:

mysql> SELECT * FROM articles
-> WHERE MATCH (title,body) AGAINST ('MySQL');
Empty set (0.00 sec)

The search result is empty because the word 「MySQL」 is present in at least 50% of the rows.
==中略==
Users who need to bypass the 50% limitation can use the boolean search mode
==============節錄完畢============