如何在SELECTION查询中使用IF条件？ [英] How do i use an IF condition in a SELECTION query?

问题描述

大家好，


我正在尝试编写一个选择查询来过滤日期的记录列表。字段值是BETWEEN最小值和最大值。这些值必须从表格中取得，如果它们不是空的。如果它们是空的，则查询必须返回整个未过滤的列表。

我不知道如何在SELECT .... WHERE函数中插入IF条件。


非常感谢您的关注

Hi everybody,

i''m trying to write a selection query that filters a list of records which the "date" field value is BETWEEN a minimum and a maximum values. These values must be taken from a form IF they are not empty. If they are empty the query must return the whole unfilterd list.
I don''t know how to insert an IF condition in a SELECT....WHERE function.

Many thanks for your attention

推荐答案

我不确定您是否可以在SQL语句中完成此操作，坦率地说，我是''不是要问的人。您可以做的是动态创建一个Query，根据名为txtDOB的表单字段是否为Null有条件地构建SQL Source语句。以下代码将基于名为tblEmployees的Employee表动态创建名为New Query的Query。如果出生日期字段（[txtDOB]）为空，则从tblEmployees返回所有记录。如果出生日期字段不为空，则返回其出生日期介于1970年1月1日至1970年12月31日之间的所有员工记录。

I''m not sure if you can accomplish this in an SQL Statement, and quite frankly, I''m not the one to ask. What you can do is to dynamically create a Query, conditionally building the SQL Source Statement based on whether or not a Form Field named txtDOB is Null or not. The following Code will dynamically create a Query named ''New Query'' based on an Employee Table named tblEmployees. If a Date of Birth Field ([txtDOB]) Is Null, then all Records are returned from tblEmployees. If the Date of Birth Field is Not Null, then all Employee Records whose whose date of Birth falls between 1/1/1970 and 12/31/1980 are returned.

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看看这个帖子，特别是帖子＃6
http://bytes.com/topic/access/answer...ria-expression

我想这可以解决你的问题。

Take a look at this thread, especially to post #6
http://bytes.com/topic/access/answer...ria-expression
I think that can manage your problem.

MMMh ..我按照你的建议尝试了这个新查询总是为空，是否是字符串太长或其他什么问题？

MMMh.. i tried this as you suggested but the new query is always empty, is it a problem with a too long string or what else?

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