重写一个WHERE子句

Z之后 查询设计。 Steve Kass 德鲁大学 joshsackett写道： I have a WHERE clause that could be an "=" or a "LIKE" depending uponif the passed variable is populated or not. I would like to know thebest way to write the WHERE clause to make it dynamically switchbetween the 2 and make best use of the indexes.CREATE TABLE myTable(ID INT PRIMARY KEY CLUSTERED, COUNTY VARCHAR(50))CREATE INDEX IDX_myTable_County ON myTable(COUNTY)DECLARE @COUNTY VARCHAR(50)SET @COUNTY = ''SANTA CLARA'' -- Could also be SET @COUNTY = NULLSELECT ID FROM myTableWHERE COUNTY LIKE (CASE WHEN @COUNTY IS NOT NULL THEN @COUNTY ELSE ''%''END)This does not seem like best practice to me because I am forced to use"LIKE" even when @COUNTY is populated with data. Ultimately I''d like:WHERE (CASE WHEN @COUNTY IS NOT NULL COUNTY = @COUNTY ELSE COUNTY LIKE''%'' END)but that is incorrect syntax on "=".Also, I do not want to use a dynamically built statement. Is there away around this?Thanks,Josh 解决方案 这篇关于重写一个WHERE子句的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！ 上岸，阿里云！