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2008-03-10 18:04
If you have ever performed a SELECT COUNT(*) on a very large table, you know how long it can take. For example, when I ran the following command on a large table I manage:
SELECT COUNT(*) from <table_name>
It took 1:09 to count 10,725,948 rows in the table. At the same time, SQL Server had to perform a lot of logical and physical I/O in order to perform the count, chewing up important SQL Server resources.
A much faster, and more efficient, way of counting row |
2008-01-23 12:31
2008-01-23 12:15
2007-12-20 15:19
When creating a distributed partitioned view in SQL Server 2000 or 2005, set the "lazy schema validation" option true for each linked server participating in your distributed partitioned views. This acts to optimize performance by ensuring that the query processor does not request meta data |
2007-11-18 13:50
[
TOP (expression) [PERCENT]
[ WITH TIES ]
]
expression
指定返回行数的数值表达式。如果指定了 PERCENT，则 expression 将隐式转换为 float 值；否则，它将转换为 bigint。
在 INSERT、UPDATE 和 DELETE 语句中，需要使用括号来分隔 TOP 中的 expression。为保证向后兼容性，支持在 SELECT 使用不包含括号的 TOP expression，但不推荐这种用法。
如果查询包含 |
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