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
赵：C 错，优化器统计信息和执行计划是两个事，统计信息的最终用途是告诉优化器 optimizer 可以对每个 SQL 去选择最好的执行计划。