SQL Server where子句使用In（）vs Wildcard

[英]SQL Server where clause using In() vs Wildcard

本文翻译自 denizemektup 查看原文 2012-03-05 578 tsql/tsql/ sql-serversql-server

Is there any performance difference between query A and query B?

查詢A和查詢B之間是否存在性能差異？

Query A

查詢A.

SELECT * FROM SomeTable
WHERE 1 = 1 AND (SomeField LIKE '[1,m][6,e][n]%')

Query B

查詢B.

SELECT * FROM SomeTable
WHERE 1 = 1 AND (SomeField IN ('16', 'Mens'))

1 个解决方案

#1

The first could be much slower. An index can't be used with LIKE unless there is a constant prefix, for example LIKE 'foo%'. The first query will therefore require a table scan. The second query however could use an index on SomeField if one is available.

第一個可能要慢得多。除非存在常量前綴，否則索引不能與LIKE一起使用，例如LIKE'foo％'。因此，第一個查詢將需要表掃描。但是，第二個查詢可以在SomeField上使用索引（如果有的話）。

The first query will also give the wrong results as it matches '1en'.

第一個查詢也會在匹配'1en'時給出錯誤的結果。

注意！

本站翻译的文章，版权归属于本站，未经许可禁止转摘，转摘请注明本文地址：https://www.itdaan.com/blog/2012/03/05/fc284b3f599c882b42aeb77ba0b01260.html。

IS NULL vs = NULL in where clause + SQL Server Using DATETIME in WHERE clause in SQL Server IN vs OR in the SQL WHERE Clause SQL join: where clause vs. on clause SQL Server using wildcard within IN converting datetime in varchar and using it in where clause in Sql server 2005 SQL Server : CASE in WHERE clause Conditional WHERE clause in SQL Server SQL Server INSERT INTO with WHERE clause SQL Server Insert with where clause