MSSQL 中索引的应用与优化（mssql所有索引）

技巧

Microsoft SQL Server uses indexes to improve the performance of selecting data from a table. An index is an organized structure that allows you to quickly retrieve data without having to scan the entire table. This post will discuss the general principles of indexing and various optimization techniques in MSSQL.

An index is an additional data structure that is stored alongside the table to provide quick access to its records. In MSSQL, indexes can be clustered, meaning that they physically arrange the records in the data file in the same order defined by the index, or non-clustered, where the physical order of the data file is irrelevant. Indexes also contain one or more key columns. When a row is inserted into an indexed table, MSSQL looks up the index key column value and appends the new data to the index.

When should you use indexes in MSSQL? Generally, when you encounter performance problems such as slow queries or excessive disk reads, this is an indication that the table might need an index. If a query requires a certain field to be searched on or ordered by, then an index should be created for that field. Additionally, if an index is used as part of a regular query, or if it is used in a view or stored procedure, then an index should be created for that field as well.

Using indexes in MSSQL also has certain optimization techniques that can be used to improve performance. For example, it is generally a good practice to create multiple composite (multi-column) indexes to cover more than one field. This can help to optimize queries that search on multiple columns. Similarly, setting the fill factor (the percentage of pages and slots filled with data) to a lower value may also help to improve query performance, as it will allow data pages to be quickly modified without the overhead of disk reads.

Finally, indexes can also be optimized by creating covering indexes, which contain all the columns required to answer a query. This technique eliminates the need for MSSQL to perform additional lookups of the base table, and can speed up the query significantly.

In conclusion, indexes are essential for optimizing queries in Microsoft SQL Server and should be used whenever possible. Mastering the optimization techniques discussed here can help you gain a significant performance boost for your database applications.