오라클 HINT
오라클 HINT Optimization Approaches and Goals – Optimization 접근과 목적 /*+ ALL_ROWS */ ALL_ROWS는 Full Table Scan을 선호하며 CBO(Cost Based Optimization)는 default로 ALL_ROWS를 선택 합니다.
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SQL>SELECT /*+ ALL_ROWS */ ename, hiredate FROM emp WHERE ename like ’%%%’ Execution Plan ---------------------------------------------------------- 0 SELECT STATEMENT Optimizer=HINT: ALL_ROWS (Cost=1 Card=5 Bytes=80) 1 0 TABLE ACCESS (FULL) OF ’EMP’ (Cost=1 Card=5 Bytes=80) |
/*+ CHOOSE */ Hint Level의 CHOOSE는 RBO(Rule Based Optimization)인지 CBO(Cost Based Optimization) 인지를 … Continue reading