MS Access VBA选择查询

Question

So first sorry for my english, my native language is german.

I have an ACCESS DB with a few Tables, the DB is filled with healing Plants, and there is one Table named "Issues" it looks like that:

Columns: ID -- Name -- Headache -- Pain -- Vomitting - and so on....

And the Columns for the indications like headache and so on, are boolean- True or False.

Now i`d like to make an query that asks the user (With a listbox in a form or so, or a Text input) to tell his indication, and then there should be a list of Substances/Plants where the Value for the indication (ColumnName) is true.

I think thats a parameter for a search in a table for columns.

Answer 1

I'd look at the design of your database. Having a table with separate columns for each issue would be a real headache to update if another issue became apparent.

I'd probably use four tables for this:

• Users : UserID (AutoNum, PK ), UserName (Text)
  
• Plants : PlantID (AutoNum, PK ), PlantName (Text)
  
• IssueList : IssueID (AutoNum, PK ), IssueDescription (Text)
  
• User_Issues : UserID (Num, PK ), PlantID (Num, PK ), IssueID (Num, PK ), HasIssue (Boolean)
  

The User_Issues table has a composite key made up each identifier from the other tables - this will ensure that a user can't have the same issue for a plant more than once.

When a new user is created a query runs to update the User_Issues table:

INSERT INTO User_Issue(PlantID, IssueID, UserID)
SELECT      PlantID, IssueID, UserID
FROM        Plants, IssueList, Users
WHERE       UserName = "Darren"

This will create a Cartesian product from the plants and issues for each user. So, for example, if you have two plants and three issues you'll get 2x3 records created - a possible 6 issues across the two plants.

This SQL will allow you to allocate an issue:

SELECT        UserName
            , PlantName
            , IssueDesc
            , HasIssue
FROM        ((
             User_Issue INNER JOIN Users ON User_Issue.UserID = Users.UserID)
                        INNER JOIN Plants ON User_Issue.PlantID = Plants.PlantID)
                        INNER JOIN IssueList ON User_Issue.IssueID = IssueList.IssueID
ORDER BY    PlantName, IssueDesc

To view the issues you just have to add WHERE HasIssue to the above SQL.

SELECT        UserName
            , PlantName
            , IssueDesc
            , HasIssue
FROM        ((
             User_Issue INNER JOIN Users ON User_Issue.UserID = Users.UserID)
                        INNER JOIN Plants ON User_Issue.PlantID = Plants.PlantID)
                        INNER JOIN IssueList ON User_Issue.IssueID = IssueList.IssueID
WHERE       HasIssue
ORDER BY    PlantName, IssueDesc