查询扩展用来放宽所返回的文本搜索结果的范围
在使用查询扩展的时候Mysql对数据和索引进行两边扫描完成搜索
-- 在在上的例子中没有使用查询扩展的时候只能返回两行
-- 现在使用返回了6行
select note_text from productnotes where Match(note_text) Against('rabbit' with query expansion)\G;
*************************** 1. row ***************************
note_text: Quantity varies, sold by the sack load.
All guaranteed to be bright and orange, and suitable for use as rabbit bait.
*************************** 2. row ***************************
note_text: Customer complaint: rabbit has been able to detect trap, food apparently less effective now.
*************************** 3. row ***************************
note_text: Customer complaint:
Circular hole in safe floor can apparently be easily cut with handsaw.
*************************** 4. row ***************************
note_text: Customer complaint:
Sticks not individually wrapped, too easy to mistakenly detonate all at once.
Recommend individual wrapping.
*************************** 5. row ***************************
note_text: Customer complaint:
Not heavy enough to generate flying stars around head of victim. If being purchased for dropping, recommend ANV02 or ANV03 instead.
*************************** 6. row ***************************
note_text: Multiple customer returns, anvils failing to drop fast enough or falling backwards on purchaser. Recommend that customer considers using heavier anvils.
6 rows in set (0.00 sec)
14.4布尔文本搜索 in boolean mode
即使没有定义fulltext索引，也可以使用它哟
select note_text from productnotes where Match(note_text) Against('rabbit' in boolean mode) \G;
*************************** 1. row ***************************
note_text: Quantity varies, sold by the sack load.
All guaranteed to be bright and orange, and suitable for use as rabbit bait.
*************************** 2. row ***************************
note_text: Customer complaint: rabbit has been able to detect trap, food apparently less effective now.
2 rows in set (0.00 sec)
-- 匹配包含 heavy 但不包含任意一repo开始的词
select note_text from productnotes where Match(note_text) Against('heavy -rope*' in boo
lean mode) \G;
*************************** 1. row ***************************
note_text: Customer complaint:
Not heavy enough to generate flying stars around head of victim. If being purchased for dropping, recommend ANV02 or ANV03 instead.
1 row in set (0.01 sec)
