Sql server 2008 SQL Server 2008-索引表的优势
在SQL Server 2008上索引表的主要优点是什么 请举例说明(如果可能的话)Sql server 2008 SQL Server 2008-索引表的优势,sql-server-2008,Sql Server 2008,在SQL Server 2008上索引表的主要优点是什么 请举例说明(如果可能的话) 谢谢你,就像给书编索引一样。如果需要快速查找,SQL Server可以执行查找,而不是从表中读取每一行 想象一下,如果你不得不在一本书中查找某些内容,却没有索引?相同的原则与为一本书编制索引相同。如果需要快速查找,SQL Server可以执行查找,而不是从表中读取每一行 想象一下,如果你不得不在一本书中查找某些内容,却没有索引?同样的原则让人想到的几个可能的优点 可用于快速定位特定行或行范围 即使索引不能直接用
谢谢你,就像给书编索引一样。如果需要快速查找,SQL Server可以执行查找,而不是从表中读取每一行
想象一下,如果你不得不在一本书中查找某些内容,却没有索引?相同的原则与为一本书编制索引相同。如果需要快速查找,SQL Server可以执行查找,而不是从表中读取每一行
想象一下,如果你不得不在一本书中查找某些内容,却没有索引?同样的原则让人想到的几个可能的优点
脑海中浮现的几个可能的优势
索引提供了一种提高数据访问查询性能的方法。假设您有一个具有不同标识列的表。将索引放在每一列上,或将查询到的列组合在一起,将提高您的响应时间 示例:您有一个包含以下列的用户表:
FirstName | LastName | ZipCode
如果要查询姓氏,请在姓氏上放置索引,例如:
SELECT * FROM User where LastName = 'SMITH'
索引可以是:
CREATE NONCLUSTERED INDEX [MyIndex] ON [User]
(
[LastName] ASC
) WITH (
PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF,
SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF,
ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON
)
ON [PRIMARY]
CREATE NONCLUSTERED INDEX [MyIndex] ON [User]
(
[LastName] ASC,
[ZipCode] ASC
) WITH (
PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF,
SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF,
ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON
)
ON [PRIMARY]
或者,如果要同时查询两列,请在两列上放置索引:
SELECT * FROM User where LastName = 'SMITH' and ZipCode = '14222'
索引可以是:
CREATE NONCLUSTERED INDEX [MyIndex] ON [User]
(
[LastName] ASC
) WITH (
PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF,
SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF,
ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON
)
ON [PRIMARY]
CREATE NONCLUSTERED INDEX [MyIndex] ON [User]
(
[LastName] ASC,
[ZipCode] ASC
) WITH (
PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF,
SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF,
ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON
)
ON [PRIMARY]
在其他条件相同的情况下,如果创建索引,查询速度会更快。但是要小心,太多的索引实际上可能会降低性能。索引提供了一种提高数据访问查询性能的方法。假设您有一个具有不同标识列的表。将索引放在每一列上,或将查询到的列组合在一起,将提高您的响应时间 示例:您有一个包含以下列的用户表:
FirstName | LastName | ZipCode
如果要查询姓氏,请在姓氏上放置索引,例如:
SELECT * FROM User where LastName = 'SMITH'
索引可以是:
CREATE NONCLUSTERED INDEX [MyIndex] ON [User]
(
[LastName] ASC
) WITH (
PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF,
SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF,
ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON
)
ON [PRIMARY]
CREATE NONCLUSTERED INDEX [MyIndex] ON [User]
(
[LastName] ASC,
[ZipCode] ASC
) WITH (
PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF,
SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF,
ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON
)
ON [PRIMARY]
或者,如果要同时查询两列,请在两列上放置索引:
SELECT * FROM User where LastName = 'SMITH' and ZipCode = '14222'
索引可以是:
CREATE NONCLUSTERED INDEX [MyIndex] ON [User]
(
[LastName] ASC
) WITH (
PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF,
SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF,
ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON
)
ON [PRIMARY]
CREATE NONCLUSTERED INDEX [MyIndex] ON [User]
(
[LastName] ASC,
[ZipCode] ASC
) WITH (
PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF,
SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF,
ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON
)
ON [PRIMARY]
在其他条件相同的情况下,如果创建索引,查询速度会更快。但是要小心,太多的索引实际上可能会降低性能。优点:
1.Index Plays major role when a data is to be searched in Bulk Records
2.When data is searched in a table , it uses "sequential search technique, which
is always a time consuming process ( Or ) it leads to wastage of time.
3.When ever finds the value, it stops the searching process
优点:
1.Index Plays major role when a data is to be searched in Bulk Records
2.When data is searched in a table , it uses "sequential search technique, which
is always a time consuming process ( Or ) it leads to wastage of time.
3.When ever finds the value, it stops the searching process
不可能。。实际上,为了理解这个概念,我面临着一些索引问题。我已经发布了,顺便说一句,这可能对其他人也有帮助..不可能。。实际上,为了理解这个概念,我面临着一些索引问题。我已经发布了,顺便说一句,这可能对其他人也有帮助。现在没有时间提出这些案例的具体例子。现在没有时间提出这些案例的具体例子。谢谢更新。。我想知道,如果我们使用非聚集索引和聚集索引,有什么好处。聚集索引实际上会在每次添加或更新记录时对表中的记录重新排序。重新排序基于索引中包含的列。如果您正在检索数据范围,这可能是有利的。维基百科上有关于这个主题的好信息:[链接]谢谢更新。。我想知道,如果我们使用非聚集索引和聚集索引,有什么好处。聚集索引实际上会在每次添加或更新记录时对表中的记录重新排序。重新排序基于索引中包含的列。如果您正在检索数据范围,这可能是有利的。维基百科上有关于这个主题的好信息:[链接]谢谢你提供的信息。你能提供更多的细节吗?谢谢你提供的信息。你能提供更多的细节吗?