锘?!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 亚洲国产精品一区二区第一页,亚洲国产激情一区二区三区,无码精品黑人一区二区三区

亚洲精品92内射,午夜福利院在线观看免费 ,亚洲av中文无码乱人伦在线视色,亚洲国产欧美国产综合在线,亚洲国产精品综合久久2007

锘?div class="header_top">
Java鐭ヨ瘑鍒嗕韓緗?- 杞繪澗瀛︿範(fàn)浠庢寮€濮嬶紒聽聽聽聽
SpringBoot+SpringSecurity+Vue+ElementPlus鏉冮檺緋葷粺瀹炴垬璇劇▼ 闇囨捈鍙戝竷        

鏈€鏂癑ava鍏ㄦ爤灝變笟瀹炴垬璇劇▼(鍏嶈垂)

AI浜哄伐鏅鴻兘瀛︿範(fàn)澶хぜ鍖?/h2>

IDEA姘鎬箙嬋€媧?/h2>

66濂梛ava瀹炴垬璇劇▼鏃犲璺鍙?/h2>

閿嬪摜寮€濮嬫敹Java瀛﹀憳鍟︼紒

Python瀛︿範(fàn)璺嚎鍥?/h2>

閿嬪摜寮€濮嬫敹Java瀛﹀憳鍟︼紒

MYSQL鎵ц璁″垝 PDF 涓嬭澆


鏃墮棿:2021-04-22 10:13鏉ユ簮:http://sh6999.cn 浣滆€?杞澆  渚墊潈涓炬姤
MYSQL鎵ц璁″垝 PDF 涓嬭澆
澶辨晥閾炬帴澶勭悊
MYSQL鎵ц璁″垝 PDF 涓嬭澆

鏈珯鏁寸悊涓嬭澆錛?/strong>
閾炬帴錛?a target="_blank">https://pan.baidu.com/s/1g4oDonLRbhmSdoWQmxIo3A 
鎻愬彇鐮侊細(xì)764z 
 
 
鐩稿叧鎴浘錛?/strong>
 
涓昏鍐呭錛?/strong>


2 rows in set (0.00 sec)
鎵ц璁″垝鐨処D 1.
id鐩稿悓錛屾墽琛岄『搴忕敱涓婅嚦涓?/div>
id涓嶅悓錛屽鏋滄槸瀛愭煡璇紝id鐨勫簭鍙蜂細(xì)閫掑錛宨d鐨勫€艱秺澶т紭鍏堢駭瓚婇珮錛岃秺鍏堣鎵ц
鎵ц璁″垝鐨剆elect_type 2.
鏌ヨ鐨勭被鍨嬶紝涓昏鏄敤浜庡尯鍒嗘櫘閫氭煡璇€佽仈鍚堟煡璇€佸瓙鏌ヨ絳夈€?/div>
SIMPLE錛氱畝鍗曠殑 select 鏌ヨ錛屾煡璇腑涓嶅寘鍚瓙鏌ヨ鎴栬€?union
PRIMARY錛氭煡璇腑鍖呭惈瀛愰儴鍒嗭紝鏈€澶栧眰鏌ヨ鍒欒鏍囪涓?primary
SUBQUERY/MATERIALIZED錛歋UBQUERY 琛ㄧず鍦?select 鎴?where 鍒楄〃涓寘鍚簡瀛愭煡璇紝MATERIALIZED錛氳〃紺?where 鍚庨潰 in 鏉?/div>
浠剁殑瀛愭煡璇?/div>
UNION錛氳〃紺?union 涓殑絎簩涓垨鍚庨潰鐨?select 璇彞
UNION RESULT錛歶nion 鐨勭粨鏋?/div>
瀵逛簬 UNION 鍜?UNION RESULT 鍙互閫氳繃涓嬮潰鐨勪緥瀛愬睍鐜幫細(xì)
EXPLAIN
SELECT * FROM users WHERE id IN(1, 2)
UNION
SELECT * FROM users WHERE id IN(3, 4);
鎵ц璁″垝鐨則able 3.
鏌ヨ娑夊強鍒扮殑琛ㄣ€?/div>
鐩存帴鏄劇ず琛ㄥ悕鎴栬€呰〃鐨勫埆鍚?/div>
<unionM,N> 鐢?ID 涓?M錛孨 鏌ヨ union 浜х敓鐨勭粨鏋?/div>
<subqueryN> 鐢?ID 涓?N 鏌ヨ浜х敓鐨勭粨鏋?/div>
鎵ц璁″垝鐨則ype 4.
璁塊棶綾誨瀷錛孲QL 鏌ヨ浼樺寲涓竴涓緢閲嶈鐨勬寚鏍囷紝緇撴灉鍊間粠濂藉埌鍧忎緷嬈℃槸錛歴ystem > const > eq_ref > ref > range > index > ALL
system錛氱郴緇熻〃錛屽皯閲忔暟鎹紝寰€寰€涓嶉渶瑕佽繘琛岀鐩業(yè)O
const錛氬父閲忚繛鎺?/div>
eq_ref錛氫富閿儲寮曪紙primary key錛夋垨鑰呴潪絀哄敮涓€绱㈠紩錛坲nique not null錛夌瓑鍊兼壂鎻?/div>
ref錛氶潪涓婚敭闈炲敮涓€绱㈠紩絳夊€兼壂鎻?/div>
range錛氳寖鍥存壂鎻?/div>
index錛氱儲寮曟爲(wèi)鎵弿
ALL錛氬叏琛ㄦ壂鎻忥紙full table scan錛?/div>
涓嬮潰閫氳繃涓句緥璇存槑銆?/div>
system
explain select * from mysql.time_zone;
涓婁緥涓紝浠庣郴緇熷簱 MySQL 鐨勭郴緇熻〃 time_zone 閲屾煡璇㈡暟鎹紝璁塊棶綾誨瀷涓?system錛岃繖浜涙暟鎹凡緇忓姞杞藉埌鍐呭瓨閲岋紝涓嶉渶瑕佽繘
琛岀鐩?IO錛岃繖綾繪壂鎻忔槸閫熷害鏈€蹇殑銆?/div>
MYSQL鎵ц璁″垝
2020騫?1鏈?6鏃?/div>
14:15
 鍒嗗尯 MYSQL鎵ц璁″垝 鐨勭 1 欏?nbsp;
explain select * from (select * from user where id=1) tmp;
鍐嶄婦涓€涓緥瀛愶紝鍐呭眰宓屽錛坈onst錛夎繑鍥炰簡涓€涓復(fù)鏃惰〃錛屽灞傚祵濂椾粠涓存椂琛ㄦ煡璇紝鍏舵壂鎻忕被鍨嬩篃鏄?system錛屼篃涓嶉渶瑕佽蛋紓佺洏 
IO錛岄€熷害瓚呭揩銆?br />
 

------鍒嗛殧綰?---------------------------
鍏蟲敞Java1234寰俊鍏紬鍙?/strong>
鎺ㄨ崘璧勬枡
锘?!-- //搴曢儴妯℃澘 -->