WHERE
a.SEQ_IN_INDEX = 1 and a.INDEX_NAME <> b.INDEX_NAME
a.SEQ_IN_INDEX = 1 and a.INDEX_NAME <> b.INDEX_NAME
2017-03-06
select
a.TABLE_SCHEMA AS '數(shù)據(jù)名',
a.TABLE_NAME AS '表名',
a.INDEX_NAME AS '索引1',
b.INDEX_NAME AS '索引2',
a.COLUMN_NAME as '重復(fù)列名'
from STATISTICS a JOIN STATISTICS b ON
a.TABLE_SCHEMA = b.TABLE_SCHEMA
AND a.TABLE_NAME = b.TABLE_NAME
AND a.SEQ_IN_INDEX = b.SEQ_IN_INDEX
AND a.COLUMN_NAME = b.COLUMN_NAME
a.TABLE_SCHEMA AS '數(shù)據(jù)名',
a.TABLE_NAME AS '表名',
a.INDEX_NAME AS '索引1',
b.INDEX_NAME AS '索引2',
a.COLUMN_NAME as '重復(fù)列名'
from STATISTICS a JOIN STATISTICS b ON
a.TABLE_SCHEMA = b.TABLE_SCHEMA
AND a.TABLE_NAME = b.TABLE_NAME
AND a.SEQ_IN_INDEX = b.SEQ_IN_INDEX
AND a.COLUMN_NAME = b.COLUMN_NAME
2017-03-06
最新回答 / 揚(yáng)州灬炒飯
這樣sql是優(yōu)化了，但開發(fā)不得累死啊，那些mybatis-pagehelper這類的插件是不是就用不起來了...得自己去寫個(gè)count總記錄的sql，再寫個(gè)優(yōu)化版的分頁查詢語句？
2017-02-25
已采納回答 / 慕仰0354868
1.雖然索引大大提高了查詢速度，同時(shí)卻會(huì)降低更新表的速度，如對(duì)表進(jìn)行INSERT、UPDATE和DELETE。因?yàn)楦卤頃r(shí)，MySQL不僅要保存數(shù)據(jù)，還要保存一下索引文件。2.建立索引會(huì)占用磁盤空間的索引文件。一般情況這個(gè)問題不太嚴(yán)重，但如果你在一個(gè)大表上創(chuàng)建了多種組合索引，索引文件的會(huì)膨脹很快。索引只是提高效率的一個(gè)因素，如果你的MySQL有大數(shù)據(jù)量的表，就需要花時(shí)間研究建立最優(yōu)秀的索引，或優(yōu)化查詢語句。
2017-02-16
