这道题的答案为什么不是BCD?而是CD

Question

You have a SQL Server 2008 installation, and you want to create a highavailability solution. What are the ideal approach(es) to solve this problem? A. Backup and restore B. Replication C. Mirroring D. Clustering

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If you haven't all the things you want,be grateful for the things you don't have that you didn't want.

Answer 1

A, B 不是标准方案, 必须 可以做以类似的效果, 但必须要额外的手段和满足一定的要求

比如A, 可以手动实现类似 Log shipping , B是表对象的, 要做到, 需要所有的对象都做(有些类似的对象是不支持的, 而且新增的对象需要手工维持)

Answer 2

主要是看怎么去评判highavailability, 正常来说, 应该是某种措施能够完全达到其效果, 不需要借助其他什么, 所以 C, D 是满足的

而 B, 很显然还要欠缺一些东西

Answer 3

You have a database table with a varchar(600) field in it. Most of the records
in the table have a null value for this field. How can you save space?
A. Move the data into a second table
B. Use sparse columns
C. Install a third-party tool on the machine to compress the data
D. Use the SQL Server 2008 Declarative Management Framework

这个为什么答案是A而不是B呢?

我觉得这里使用稀疏列才正确,毕竟题目中已经说了Most of the column is null

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If you haven't all the things you want,be grateful for the things you don't have that you didn't want.

Answer 4

Most of the records in the table have a null value for this field.

你哪里看到Most of the columns了？ 稀疏列是用于多个列，很多列为空的情况。

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想不想时已是想，不如不想都不想。

Answer 5

From BOL:

The SQL Server Database Engine uses the SPARSE keyword in a column definition to
optimize the storage of values in that column. Therefore, when the column value
is NULL for any row in the table, the values require no storage.