以前没有注意过这个问题,今天群里的朋友问了这个问题,发上来给大家看看:创建一个文件a.sql:select * from t2 start with root_id 0 connect by prior id root_id; /*zhushi*/到sqlplus中执行:SQL> a.sql3 ;select * from t2 start with root_id 0 connect by prior id…
什么是SSID/ESSID/BSSID? SSID(Service Set Identifier)AP唯一的ID码,用来区分不同的网络,最多可以有32个字符,无线终端和AP的SSID必须相同方可通信。无线网卡设置了不同的SSID就可以进入不同网络ÿ…
查看执行计划的方法Explain Plan For SQL不实际执行SQL语句,生成的计划未必是真实执行的计划必须要有plan_tableSQLPLUS AUTOTRACE除set autotrace traceonly explain外均实际执行SQL,但仍未必是真实计划必须要有plan_tableSQL TRACE需要启用10046戒者SQ…
第5章 发送和接收数据 There is nomagic: any programs that exchange information must agree on how that information will be encoded—represented as a sequence of bits—as well as which program sends what information when, and how the information received affe…
转换日期有点问题。column trans_low format a20column trans_high format a20column data_default format a20SELECT--owner,-- table_name,column_name,data_type,data_length,nullable,num_distinct,density,sample_size,CASEWHEN data_type IN (CHAR, VARCHAR2)THE…