數(shù)據(jù)庫開發(fā)規(guī)范(文件)
【正文】 WHERE = )?！餝ELECT ... FROM emp E WHERE NOT EXISTS ( SELECT 39。)。MELBOURNE39。 SELECT ... FROM emp WHERE TO_NUMBER(emp_type) = 123。1） 頻繁查詢不超過大表1%~15%的場合。執(zhí)行計劃 0 SELECT STATEMENT Optimizer=CHOOSE 1 0 TABLE ACCESS (FULL) OF 39。 SQL Trace開始SQL ALTER SESSION SET SQL_TRACE = true。%dump_dest39。 SQL Trace結束SQL ALTER SESSION SET SQL_TRACE = false。統(tǒng)計 0 recursive calls 12 db block gets 4 consistent gets 0 physical reads 0 redo size 4779 bytes sent via SQL*Net to client 314 bytes received via SQL*Net from client 1 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 0 rows processed SQL TKPROF 初始化afe57gc2/oracle/product/ 40 sqlplus /SQL ALTER SESSION SET TIMED_STATISTICS = true?！ 。篠QL grant plustrace to ops$ino。12339?！?SELECT ... FROM location WHERE loc_id IN (10, 20, 30)。MELBOURNE39。 FROM dept WHERE dept_no = AND dept_cat = 39。A39?！餝ELECT dept_no, dept_name FROM dept D WHERE EXISTS ( SELECT 39。 FROM dept WHERE dept_no = AND dept_cat = 39?！餝ELECT ... FROM emp E WHERE = 39。MANAGER39。A39。A39?！餝ELECT emp_name FROM emp WHERE emp_cat = (SELECT MAX(category) FROM emp_categories) AND sal_range = (SELECT MAX(sal_range) FROM emp_categories) AND emp_dept = 0020。SYDNEY39。SYDNEY39。 表的行計數(shù)SELECT COUNT(有索引的列) FROM TRANS。SMITH%39。X39。SMITH%39。A39。AMEXA39?！ ?SELECT acc_name, trans_date, amount FROM transaction WHERE amount 0。CAPITAL39。 3）減少訪問次數(shù)SELECT emp_name, sal, grade FROM emp WHERE emp_no = 0342。) OR 25 (SELECT COUNT(*) FROM EMP WHERE emp_mgr = )。MANAGER39。 AND 25 (SELECT COUNT(*) FROM EMP WHERE emp_mgr = )。2）3張表連接 SELECT * FROM EMP E, LOC L, CAT C WHERE BETWEEN 1000 AND 2000 AND = AND = 。表關聯(lián)條件放在語句的最后部。比如：保留10天數(shù)據(jù)，每天刪除10天前的一天數(shù)據(jù)，在刪除數(shù)據(jù)的時候，可以采用采用alter table table_name truncate partitio
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