这三个函数在不同的数据库中可能有略微不同的语法和用法，但它们的基本功能如下：1：ISNULL：用于检查一个表达式是否为NULL，并返回布尔值（TRUE或FALSE）。如果表达式为NULL，则ISNULL返回TRUE；否则返回FALSE。例如，SQL Server中使用ISNULL函数将一个空值替换为另一个值：SELECT ISNULL(ProductName, '我是被替换的值') AS Pro....

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更新时间 2024-06-13 15:27:07

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