It permits fast range lookup and sort order . smaller index keys take less space and are more effective that larger keys 与较大的键相比，较小的索引键占用的空间更小，并且更为有效。
In this way , you will have all columns needed to cover the query , but the index key itself is small and efficient 这样，将具有覆盖查询所需的所有列，但索引键本身较小，而且效率高。
When locking rows or index key ranges , the database engine places an intent lock on the pages containing the rows or keys 当锁定行或索引键范围时，数据库引擎将在包含行或键的页上放置意向锁。
It should be noted that the db2 index key size limit is 1024 bytes , and the index key limit includes all overhead bytes 应该注意， db2索引键的大小限制为1024字节，而且索引键限制包括占用的所有字节。
Redesign nonclustered indexes with a large index key size so that only columns used for searching and lookups are key columns 重新设计索引键大小较大的非聚集索引，以便只有用于搜索和查找的列为键列。
The maximum allowed size of the combined column values can exceed the 900 - byte limit that is imposed on the index key value 允许的组合列值最大大小可以超过900字节的限制（对索引键值强制实施该限制） 。
When you create indexes on varchar or vargraphic columns in your unicode tables , you need to pay attention of the index key limit 在unicode表中的varchar或vargraphic列上创建索引时，需要注意索引键限制。
Any column or combination of columns that is eligible as an index key is eligible for statistics , with the following exceptions 对于任何可以作为索引键的列或列的组合，都可以创建统计信息，但以下情况除外：
In this way , the index key size would be 110 bytes 55 2 , and the index would still contain all the required columns 这样，索引键大小将为110个字节( 55 * 2 ) ，并且索引仍将包含所需的所有列。下面的语句就创建了这样的索引。
Lock hints rowlock , updlock , and xlock that acquire row - level locks may place locks on index keys rather than the actual data rows 获取行级别锁的锁提示rowlock 、 updlock和xlock ，则可能对索引键而不是实际的数据行采用锁。
