摘要:
1. 预执行 explain plan for 实际并没有执行SQL语句。 SQL> explain plan for select ca_cstid from c_acc; Explained. SQL> @?/rdbms/admin/utlxpls PLAN_TABLE_OUTPUT-------------------------------------------------------... 阅读全文
摘要:
overviewOracle's cost-based optimizer (COB) uses statistics to calculate the selectivity (the fraction of rows in a table that the SQL statement's pre... 阅读全文