sql query to get count

Original address: http://www.cnblogs.com/lyhabc/p/3367274.htmlBefore reading this article, you can read the following article firstSQL Server's unique task scheduling algorithm "Sqlos"Task Scheduler for SQL Server Sqlos [go]Translated

Read SQL Server query planRead Catalogue Begin How SQL Server looks for records SQL Server Join method More specific execution procedures Index statistics: The choice of the query plan is based on Optimizing View Queries

Read Catalogue Begin How SQL Server looks for records SQL Server Join method More specific execution procedures Index statistics: The choice of the query plan is based on Optimizing View Queries Recommended

First, the practical, the misunderstanding of the use of the indexThe purpose of the theory is to apply. Although we have just listed when clustered or nonclustered indexes should be used, in practice the above rules are easily overlooked or cannot

For more information about bugs fixed in SQL Server 2000 Service Pack 4, click the following article number to view the article in the Microsoft Knowledge Base:314128 FIX: When an RPC call is performed, Access with conflicting values includes an

Optimizing queries can be a common thing for SQL Server optimizations. Since the optimization of database is a wide topic in itself, this article only talks about how to understand SQL Server query plan when optimizing query. After all, my knowledge

SQL tuning is primarily about reducing the number of consistent gets and physical reads. COUNT (1) is compared with COUNT (*): If your datasheet does not have a primary key, then count (1) is faster than COUNT (*)If you have a primary key, the

In DB2, the sum function used to replace the count query is to calculate and sum the column values. The www.2cto.com count function accumulates the columns that meet the conditions and adds one when the conditions are met. The count function is

To analyze the performance of a query, you can view {Tagshow (event, '% D6 % B4 % D0 % D0 % BC % C6 % BB % AE ');} "Href =" javascript:; "target =" _ Self ">Execution Plan. Execution Plan description {Tagshow (event, 'SQL ');} "Href =" javascript:; "

Today to see a Bo Friends of the article, feel good, reprint, hope to help you, more articles, please visit: http://blog.haoitsoft.com1, no index or no index (this is the most common problem of slow query, is the defect of program design)2, I/O