Mysql innodbÒýÇæºÍmyisamÒýÇæ ʹÓÃË÷ÒýÇø±ð
Ê×ÏÈÄãÒªÀí½â,innodbµÄÖ÷¼üË÷Òý¶¼ÊǾ۴ØË÷Òý,ËüµÄ¸¨ÖúË÷ÒýÀïÃ涼°üº¬ÓбíµÄÖ÷¼ü,¶øÇÒÖ÷¼ü¶¼ÔÚ¸¨ÖúË÷ÒýµÄ×îºóÒ»ÁÐ.¶ømyisamµÄË÷Òý,¶¼ÊÇÆÕͨË÷Òý,´æ´¢µÄÊÇÁеÄÖµ,»¹ÓÐÁÐÔÚÔ±íÖеĵØÖ·Öµ---²»´æ´¢Ö÷¼üÖµ.
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CREATE TABLE `innodb` ( `id` int(10) UNSIGNED
NOT NULL, `a` int(11) DEFAULT NULL, PRIMARY KEY (`id`), KEY `a` (`a`))
ENGINE=InnoDB DEFAULT CHARSET=latin1;
CREATE TABLE `myisam` (`id` int(10) UNSIGNED NOT NULL, `a` int(11)
DEFAULT NULL, PRIMARY KEY (`id`), KEY `a` (`a`)) ENGINE=myisam DEFAULT
CHARSET=latin1;
mysql> EXPLAIN SELECT * from innodb ORDER BY id \G
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
TABLE: pktest
type: INDEX------
innodbÊǾ۴ØË÷Òý,ËùÒÔmysqlÖ±½ÓɨÃèprimary key²¢È¡³öËùÓеÄ×Ö¶Î.ÐèÒªÓõ½primary key,´Ë´¦Ö±½ÓɨÃèË÷Òý,¶ø²»ÐèÒª²éÕÒ±í,±ÈALL¸ü¿ì
possible_keys: NULL
KEY: PRIMARY ----Óɴ˿ɼû,keyµÄÄÚÈݲ¢²»Ò»¶¨ÔÚpossible keysÖÐ
key_len: 4
ref: NULL
rows: 6
Extra:---ÕâÀïΪºÎ²»ÏÔʾΪusing indexÄØ?
1 row IN SET (0.00 sec)
mysql> EXPLAIN SELECT * from myisam ORDER BY id \G
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
TABLE: myisam
type: ALL-----
myisamÊÇÆÕͨµÄË÷Òý,Ö»ÊÇÔÚË÷ÒýÖд洢ÁËÐеÄrowid,´ËË÷ÒýµÄidÁÐÓ¦¸ÃÊÇÓÐÐòµÄ.µ«ÊÇͨ¹ýidÁÐÈ¥¶¨Î»µ½Ô±íµÄrowid,È»ºóÓÉrowid²éÕÒ±íµÄËùÓÐ×Ö¶Î,»á´øÀ´´óÁ¿µÄËæ»ú¶Á.´ËʱÓÅ»¯Æ÷Ñ¡ÔñÁËÖ±½Ó¶ÁÈ¡Ô±íÅÅÐòµÄ·½·¨,ûÓÐÀûÓÃÈκÎË÷Òý.
possible_keys: NULL
KEY: NULL
key_len: NULL
ref: NULL
rows: 6
Extra: USING filesort----
ÓÐfilesort³öÏÖ,È«±íɨÃèÒÔºó,ÔÙÅÅÐò
1 row IN SET (0.00 sec)
mysql> EXPLAIN SELECT id from innodb WHERE a=3 \G
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
TABLE: innodb
type: ref
possible_keys: a
KEY: a
key_len: 5
ref: const
rows: 1
Extra: USING WHERE; USING INDEX----
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