熊猫的非唯一索引对性能有什么影响?。
What is the performance impact of non-unique indexes in pandas?
因为其是一个唯一索引扫描，所以在访问路径图中不显示FETCH或表节点。
There is no FETCH or table node shown in the access path graph because it is an index-only scan.
原表需要一个主键或则唯一索引，因为删除的触发器需要，否则数据不会被复制。
The new table 'test'. '_online_table_new' does not have a PRIMARY KEY or a unique index which is required for the DELETE trigger.
与RDBMS索引相似，可以使用多个属性创建复合索引，也可创建唯一索引，确保不存在重复的值。
Like RDBMS indexes, you can create compound indexes using multiple attributes, and unique indexes, which ensure that duplicate values are not allowed.
如果一个以上的资料列中的某单一资料行为NULL，您将无法建立该单一资料行的唯一索引。
You cannot create a unique index on a single column if that column contains NULL in more than one row.
同样地，如果一个以上的资料列中的一组资料行全为NULL的话，您将无法在该组资料行上建立唯一索引。
Similarly, you cannot create a unique index on multiple columns if the combination of columns contains NULL in more than one row.
从性能的角度来看，这被认为是一个非常有效的联接操作，因为通过贯穿唯一索引的唯一访问扫描内部表的成本是最优的。
From the performance perspective, this is considered a very efficient join operation, because the cost for scanning the inner table is optimal via unique access through a unique index.
Oracle学习参考，包括ROWID的概念、索引的概念、唯一索引、组合索引、位图索引和 基于函数的索引等。
Oracle Learning Resources, including the ROWID of the concept, the concept of indexing, unique indexes, composite indexes, bitmap indexes and function-based indexes.
通常情况下，在基础索引提供好处(如唯一索引访问、避免排序或一些类似的好处)时，可通过优化器选择非匹配索引扫描。
Typically, a non-matching index scan is chosen by the optimizer when the underlying index provides benefits such as index-only access, avoids sort, or some similar benefit.
然后它会使用可搜索的加密模式对索引进行加密，用基于属性的加密模式以恰当的手段对唯一密钥加密。
It then encrypts the index using a searchable encryption scheme and encrypts the unique key with an attribute-based encryption scheme under an appropriate policy.
但是，如果会话数据与某个新索引冲突(比如重复行在唯一的索引上冲突)，则在数据纠正之前不会为该会话物化该索引。
However, if the session data conflicts with a new index, (such as duplicate rows conflicting with a unique index), the index is not materialized for that session until the data is corrected.
这些词典可以从特殊的索引实现，而索引又需要唯一元素名称。
These lexicons can be implemented from special indexes, which in turn can require unique element names.
编码每个纬度和经度可能导致索引大量唯一的词汇，这取决于应用程序。
Depending on the application, encoding every latitude and longitude can result in a large number of unique terms to be indexed.
对于那些不是唯一的索引，索引键的数量要少于记录的数量。
For indexes that are not unique, the number of index keys is less than the number of records.
可选地，定义索引来优化查询和保证唯一性。
Indexes are defined to optimize queries and, optionally, to guarantee uniqueness.
当我们系统的看这些，不应该装的物品时，唯一改变的是索引值。
As we've seen systematically in the don 't-takes, the only thing that gets changed is the index.
然而，由于xml列不属于表分区键的一部分，任何唯一xml值索引必须创建为全局索引。
However, since XML columns cannot be part of the table partitioning key, any unique XML values index will have to be created as a global index.
例如，非唯一元素能够阻止您正确评估执行较少索引查询的代码。
For example, non-unique element names can keep you from properly evaluating code that performs fewer index look-ups.
为了高速缓存一个来自Web服务的响应，您需要生成一个用来对它进行索引的唯一的密钥。
To cache a response from a web service, you need to generate a unique key to use for indexing it.
我们将其中一人的地址键入Facebook搜索引擎，于是就得到了唯一一个符合条件的Facebook个人资料。
We typed the address of one of them into the Facebook search engine and it came back with only one Facebook profile matching that address.
首先为其建立索引，并使用对称的加密模式(例如aes)以唯一的密钥对其进行加密。
Begins by indexing it and encrypting it with a symmetric encryption scheme (e.g., AES) under a unique key.
Stocky说，将实时搜索结果集成到Goole搜索引擎中的唯一问题是要知道用户什么时候不需要这些结果。
Stocky says the only problem with including real-time results into the Google search engine is knowing when people don't want them.
就现在来说，Google的用户们并没有抛弃Google，将Bing当作唯一的搜索引擎来使用，而Bing的用户也没有对Bing死心塌地，忠诚不二。
As of now, Google's users aren't running away from the service and making Bing their exclusive search engine, and neither are Bing's users completely loyal to their service.
为每一行数据所创建的索引成为了计数器，因为每当新的一行数据加进来的时候，这个索引是唯一的增量，这也意味着计数器将与字符串数据的总量同步变化。
The index created for each row of data becomes the count because it was only incremented when a new row of data was found, meaning it is in sync with the amount of data in the string.
在每一个物理计算机上给每一个LPAR分配一个唯一的GUID索引，以区分使用InfiniBand的不同LPAR。
Assign each LPAR a unique GUID index within each physical computer to distinguish the different LPARs using InfiniBand.
最后，然而，唯一条件是在B2B搜索引擎优化的问题是那些实际使用你的前景。
In the end, however, the only terms that matter in B2B SEO are those your prospects actually use.
唯一的限制将是您的网站是否是正确地在互联网上搜索引擎的位置。
The only constraint will be whether your website is correctly positioned on the web's search engines.
一个称为索引或注标的唯一号码，会与共用变数名称结合，用以分辨阵列中的每个元素。
A unique number, called an index or subscript, combined with the Shared variable name distinguishes each element in the array.
因为你已经确定我推断是三列以确定唯一性(主题行，主体和发件人地址)，所以您将创建包含所有三列的索引。
As you've identified what I infer to be three columns to determine uniqueness (subject line, body, and sender address) you'll create the index to include all three columns.
因为你已经确定我推断是三列以确定唯一性(主题行，主体和发件人地址)，所以您将创建包含所有三列的索引。
As you've identified what I infer to be three columns to determine uniqueness (subject line, body, and sender address) you'll create the index to include all three columns.
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