我对DB的接触有限，只是作为应用程序程序员使用过DB。我想知道关于聚集和非聚集索引。
我在谷歌上搜索了一下，我发现:
A clustered index is a special type of index that reorders the way
records in the table are physically
stored. Therefore table can have only
one clustered index. The leaf nodes
of a clustered index contain the data
pages. A nonclustered index is a
special type of index in which the
logical order of the index does not
match the physical stored order of
the rows on disk. The leaf node of a
nonclustered index does not consist of
the data pages. Instead, the leaf
nodes contain index rows.
我在SO中发现的是聚集索引和非聚集索引之间的区别是什么?
有人能用通俗易懂的语言解释一下吗?
聚集索引
聚集索引根据表或视图中的键值对数据行进行排序和存储。这些是包含在索引定义中的列。每个表只能有一个聚集索引，因为数据行本身只能按一种顺序排序。
只有当表中包含聚集索引时，表中的数据行才会按排序顺序存储。当一个表具有聚集索引时，这个表称为聚集表。如果表没有聚集索引，则其数据行存储在称为堆的无序结构中。
非聚集
Nonclustered indexes have a structure separate from the data rows. A nonclustered index contains the nonclustered index key values and each key value entry has a pointer to the data row that contains the key value.
The pointer from an index row in a nonclustered index to a data row is called a row locator. The structure of the row locator depends on whether the data pages are stored in a heap or a clustered table. For a heap, a row locator is a pointer to the row. For a clustered table, the row locator is the clustered index key.
可以将非键列添加到非聚集索引的叶级，以绕过现有的索引键限制，并执行完全覆盖的索引查询。有关更多信息，请参见创建包含列的索引。有关索引键限制的详细信息，请参见SQL Server最大容量规格。
参考:https://learn.microsoft.com/en-us/sql/relational-databases/indexes/clustered-and-nonclustered-indexes-described
聚集索引——聚集索引定义了数据在表中物理存储的顺序。表数据只能按某种方式排序，因此，每个表只能有一个聚集索引。在SQL Server中，主键约束自动在特定列上创建聚集索引。
Non-Clustered Index - A non-clustered index doesn’t sort the physical data inside the table. In fact, a non-clustered index is stored at one place and table data is stored in another place. This is similar to a textbook where the book content is located in one place and the index is located in another. This allows for more than one non-clustered index per table.It is important to mention here that inside the table the data will be sorted by a clustered index. However, inside the non-clustered index data is stored in the specified order. The index contains column values on which the index is created and the address of the record that the column value belongs to.When a query is issued against a column on which the index is created, the database will first go to the index and look for the address of the corresponding row in the table. It will then go to that row address and fetch other column values. It is due to this additional step that non-clustered indexes are slower than clustered indexes
聚类索引和非聚类索引的区别
每个表只能有一个聚集索引。但是，你可以
在一个表上创建多个非聚集索引。
聚集索引只对表进行排序。因此，他们不消费
额外的存储。非聚集索引存储在单独的位置
从实际表中占用更多的存储空间。
聚集索引比非聚集索引快，因为它们
不要涉及任何额外的查找步骤。
有关更多信息，请参阅本文。
