Which three are true about Optimizer Statistics?
A)They can be gathered manually
B)They are automatically updated by DML statements
C)They contain the execution plan for each executed SQL statement.
D)They include the number of rows in a table and the number of distinct values per column.
E)They can be gathered automatically by an automatic maintenance job.
Answer: ADE
趙：C 錯，優化器統計信息和執行計劃是兩個事，統計信息的最終用途是告訴優化器 optimizer 可以對每個 SQL 去選擇最好的執行計劃。