MS Access：如果为空，则忽略查询条件

Question

我在 Access 中有一个表单，我在其中运行基于多个文本框的查询。我对从文本框拉出的几个查询字段应用条件，但希望当文本框为空白时查询忽略条件。

例如，如果 Machine_TextBox 为空，则不要将条件应用于 Events.Machine 字段。

SQL代码是：

SELECT Events.Machine, Events.[Event Date], Events.[Event Description],
Events.[Action Taken], Events.[Machine Clinical], Events.[Modalities Not Clinical],
Events.[Manufacturer Ticket #], Events.[TLC Ticket #], Events.FSR, Events.ID, 
Events.[Event Recorded By], Events.[Action Recorded By], Events.[Downtime Validation],
Events.[Event Time]  

FROM Events

WHERE (((Events.Machine)=IIf([Forms]![SearchEvent]![Machine_TextBox] Is Null,"",
[Forms]![SearchEvent]![Machine_TextBox]))  AND ((Events.[Event Date]) Between 
Nz([Forms]![SearchEvent]![StartDate_TextBox],#1/1/1900#) And Nz([Forms]![SearchEvent]![EndDate_TextBox],#1/1/2100#))  
AND ((Events.[Event Description]) Like "*" & [Forms]![SearchEvent]![EventDetails_TextBox])  
AND ((Events.[Manufacturer Ticket #])=[Forms]![SearchEvent]![Manufacturer_TextBox])  
AND ((Events.[TLC Ticket #])=[Forms]![SearchEvent]![TLC_TextBox]) 
AND ((Events.FSR)=[Forms]![SearchEvent]![FSR_TextBox]))  
OR (((Events.Machine)=IIf([Forms]![SearchEvent]![Machine_TextBox] Is Null,"",[Forms]![SearchEvent]![Machine_TextBox]))  
AND ((Events.[Event Date]) Between Nz([Forms]![SearchEvent]![StartDate_TextBox],#1/1/1900#) 
AND Nz([Forms]![SearchEvent]![EndDate_TextBox],#1/1/2100#))  
AND ((Events.[Action Taken]) Like "*" & [Forms]![SearchEvent]![EventDetails_TextBox])  
AND ((Events.[Manufacturer Ticket #])=[Forms]![SearchEvent]![Manufacturer_TextBox]) 
AND ((Events.[TLC Ticket #])=[Forms]![SearchEvent]![TLC_TextBox])  
AND ((Events.FSR)=[Forms]![SearchEvent]![FSR_TextBox]))

ORDER BY Events.[Date and Time Stamp] DESC;

此致，

标记

Answer 1

您可以尝试这里描述的技术。

对于每个搜索框，使用布尔逻辑来过滤其值，或者通过使 AND 子句为 TRUE 来忽略此 AND 子句（如果它为空）。

我将仅使用两个搜索框作为示例：

SELECT stuff
FROM Events

WHERE ((Events.Machine = [Forms]![SearchEvent]![Machine_TextBox]) 
            OR ([Forms]![SearchEvent]![Machine_TextBox] Is Null))
  AND ((Events.[Event Description] Like "*" & [Forms]![SearchEvent]![EventDetails_TextBox] & "*") 
            OR ([Forms]![SearchEvent]![EventDetails_TextBox] Is Null))
  AND ...