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POHow can i design a DB where the user can define the fields and types of a detail table in a M-D relationship?
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2010-06-01T17:23:24.013
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2010-06-01T17:27:00.933
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My application has one table called 'events' and each event has approx 30 standard fields, but also user defined fields that could be any name or type, in an 'eventdata' table. Users can define these event data tables, by specifying x number of fields (either text/double/datetime/boolean) and the names of these fields. This 'eventdata' (table) can be different for each 'event'. My current approach is to create a lookup table for the definitions. So if i need to query all 'event' and 'eventdata' per record, i do so in a M-D relaitionship using two queries (i.e. select * from events, then for each record in 'events', select * from 'some table'). Is there a better approach to doing this? I have implemented this so far, but most of my queries require two distinct calls to the DB - i cannot simply join my master 'events' table with different 'eventdata' tables for each record in in 'events'. I guess my main question is: can i join my master table with different detail tables for each record? E.g. <pre><code>SELECT E.*, E.Tablename FROM events E LEFT JOIN 'E.tablename' T ON E._ID = T.ID </code></pre> If not, is there a better way to design my database considering i have no idea on how many user defined fields there may be and what type they will be. 
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How can i design a DB where the user can define the fields and types of a detail table in a M-D relationship?
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1. COThanks to all the suggestions. All have given me something to think about. The current implementation is a little ugly, but is still reasonably manageable with the rules/restrictions i currently have. I think i will either leave as is, or go with the limit of say 30 fields of all types string and use the group_cat() function of mysql. The only downside of this is the inability to filter by value/datetime in the eventdata table and the lookup of each customdata fieldname per event. Both methods have adv/disadv. Unfortunately i think noSQL is not going to be easy in my IDE/dev scenario.
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 POHow can i design a DB where the user can define the fields and types of a detail table in a M-D relationship?
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A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.