从表中的语句花费一个小时很简单

Question

我有这条简单的线：var records = db.MyDbTable.Where(x => x.SupplierId.HasValue).ToList();而且执行需要一个小时。我表中有272行。该表有一列，NVARCHAR(MAX)里面有巨大的字符串。如何优化语句？之后在代码中，我有一个foreach，它会遍历记录并对其进行处理。db中的select语句需要5分钟。当我使用SQL事件探查器进行检查时，这是从C＃转换而来的语句：SELECT     [Extent1].[id] AS [id],     [Extent1].[xml] AS [xml],     [Extent1].[name] AS [name],     [Extent1].[create] AS [create],     [Extent1].[sale] AS [sale],     [Extent1].[SupplierId] AS [SupplierId],     [Extent1].[Success] AS [Success],     [Extent1].[IId] AS [IId]    FROM [dbo].[MyDbTable] AS [Extent1]    WHERE [Extent1].[SupplierId] IS NOT NULL

Answer 1

尝试在数据库中的where字段（SupplierId）上添加索引，看看是否有帮助。