Slide 41
Slide 41 text
࣮ߦܭը
mysql> EXPLAIN SELECT * FROM Country, (SELECT * FROM City WHERE Population > 1000000) AS C1 WHERE Country.Code =
C1.CountryCode;
+----+-------------+------------+--------+---------------+---------+---------+----------------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+------------+--------+---------------+---------+---------+----------------+------+-------------+
| 1 | PRIMARY | | ALL | NULL | NULL | NULL | NULL | 237 | |
| 1 | PRIMARY | Country | eq_ref | PRIMARY | PRIMARY | 3 | C1.CountryCode | 1 | |
| 2 | DERIVED | City | ALL | NULL | NULL | NULL | NULL | 4079 | Using where |
+----+-------------+------------+--------+---------------+---------+---------+----------------+------+-------------+
3 rows in set (0.00 sec)
Ҿ༻ݩ:MySQLͷEXPLAINΛపఈղઆ!!
http://nippondanji.blogspot.jp/2009/03/mysqlexplain.html
ɾUZQF
ϨίʔυΞΫηελΠϓɻ
ཁ*/%&9ͷར༻ͷ༗ແ͍ํΛදͨ͠ͷ
ɾओͳछྨ
DPOTUɾɾɾ13*."3:,&:·ͨ6/*26&ΠϯσοΫεͷϧοΫΞοϓʹΑΔΞΫηεɻ࠷ɻ
FR@SFGɾɾɾ+0*/ʹ͓͍ͯ13*"3:,&:·ͨ6/*26&,&:͕ར༻͞ΕΔ࣌ͷΞΫηελΠϓɻDPOTUͱࣅ͍ͯΔ͕+0*/
Ͱ༻͍ΒΕΔͱ͜Ζ͕ҧ͏ɻ
SFGɾɾɾϢχʔΫʢ13*."3:PS6/*26&ʣͰͳ͍ΠϯσοΫεΛͬͯՁݕࡧʢ8)&3&LFZWBMVFʣΛߦͬͨ
࣌ʹΘΕΔΞΫηελΠϓɻ
SBOHFɾɾɾΠϯσοΫεΛ༻͍ͨൣғݕࡧɻ
JOEFYɾɾɾϑϧΠϯσοΫεεΩϟϯɻΠϯσοΫεશମΛεΩϟϯ͢Δඞཁ͕͋ΔͷͰͱ͍ͯɻ
"--ɾɾɾϑϧςʔϒϧεΩϟϯɻΠϯσοΫε͕·ͬͨ͘ར༻͞Ε͍ͯͳ͍͜ͱΛࣔ͢ɻ0-51ܥͷॲཧͰվળඞਢɻ