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。
原文：https://blog.51cto.com/13854012/2424451