索引键

• For indexes , the insertion point of a new row is set by the index key
  对于索引，新行的插入点由索引键设置。
• Maximum size of index keys
  索引键的最大大小
• If the index key size exceeds 900 bytes , a warning message is displayed
  如果索引键大小超过900字节，会显示一条警告消息。
• All the columns in a composite index key must be in the same table or view
  组合索引键中的所有列必须在同一个表或视图中。
• Foreign key table
  外部索引键数据表
• Columns that are not part of the index key can be included in nonclustered indexes
  可以将不属于索引键的列包含在非聚集索引中。
• Index key size
  索引键大小
• These columns are not considered by the database engine when calculating the index key size
  计算索引键大小时，数据库引擎不考虑这些列。
• The index key size limit also applies to those constraints that are enforced through indexes
  索引键大小限制也应用于通过索引施加的那些约束。
• The index key limit might be reduced when you are using varchar or vargraphic data type
  当使用varchar或vargraphic数据类型时，索引键限制可能减少。