为什么查询语句中经常会有"1=1"

目的是动态查询，查询语句先加上WHERE 1=1，然后后面的条件不论是有一个或者多个都可以直接写为AND <condition>.

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dim sqlstmt as new StringBuildersqlstmt.add("SELECT * FROM Products")sqlstmt.add(" WHERE 1=1") ''// From now on you don't have to worry if you must ''// append AND or WHERE because you know the WHERE is thereIf ProductCategoryID <> 0 then  sqlstmt.AppendFormat(" AND ProductCategoryID = {0}", trim(ProductCategoryID))end ifIf MinimunPrice > 0 then  sqlstmt.AppendFormat(" AND Price >= {0}", trim(MinimunPrice))end if

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http://stackoverflow.com/questions/242822/why-would-someone-use-where-1-1-and-conditions-in-a-sql-clause