About me:Oracle ACE pro,optimistic,passionate and harmonious. Focus on ORACLE,MySQL and other database programming,peformance tuning,db design, j2ee,Linux/AIX,Architecture tech,etc
全部博文(191)
发布时间:2023-05-08 15:41:01
rownum是oracle中的一个伪列(pseudo column),其目的就是给查询出来的结果集标注行号。可以实现查询前n行(top-n),中间几行(middle-n),最后几行(bottom-n)的功能。但是rownum又是一个很特殊的列,使用过程中,首先要弄清楚oracle rownum的原理,然后加以分析。......【阅读全文】
发布时间:2023-05-08 15:33:16
? 对于不在同一层的,不能直接用HINTS来访问,比如这个例子的子查询b与a不在同一层,内部使用query block实现,诸如SEL$n,DEL$n,UPD$n,MRG$n,然后用@query_block访问,如例子中的LEADING(@"SEL$5DA710D3" "B"@"SEL$2" "A"@"SEL$1")......【阅读全文】
吻的感觉适2025-07-18 23:11
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