How to Design a Database for User Defined Fields

How to design a database for User Defined Fields?

If performance is the primary concern, I would go with #6... a table per UDF (really, this is a variant of #2). This answer is specifically tailored to this situation and the description of the data distribution and access patterns described.

Pros:

1. Because you indicate that some UDFs
   have values for a small portion of
   the overall data set, a separate
   table would give you the best
   performance because that table will
   be only as large as it needs to be
   to support the UDF. The same holds true for the related indices.

2. You also get a speed boost by limiting the amount of data that has to be processed for aggregations or other transformations. Splitting the data out into multiple tables lets you perform some of the aggregating and other statistical analysis on the UDF data, then join that result to the master table via foreign key to get the non-aggregated attributes.

3. You can use table/column names that
   reflect what the data actually is.

4. You have complete control to use data types,
   check constraints, default values, etc.
   to define the data domains. Don't underestimate the performance hit resulting from on-the-fly data type conversion. Such
   constraints also help RDBMS query
   optimizers develop more effective
   plans.

5. Should you ever need to use foreign
   keys, built-in declarative
   referential
   integrity is rarely out-performed by
   trigger-based or application level
   constraint enforcement.

Cons:

1. This could create a lot of tables.
   Enforcing schema separation and/or a
   naming convention would alleviate
   this.

2. There is more application code
   needed to operate the UDF definition
   and management. I expect this is
   still less code needed than for the
   original options 1, 3, & 4.

Other Considerations:

1. If there is anything about the
   nature of the data that would make
   sense for the UDFs to be grouped,
   that should be encouraged. That way,
   those data elements can be combined
   into a single table. For example,
   let's say you have UDFs for color,
   size, and cost. The tendency in the
   data is that most instances of this
   data looks like

    'red', 'large', 45.03 
   

   rather than

    NULL, 'medium', NULL
   

   In such a case, you won't incur a
   noticeable speed penalty by
   combining the 3 columns in 1 table
   because few values would be NULL and
   you avoid making 2 more tables,
   which is 2 fewer joins needed when
   you need to access all 3 columns.

2. If you hit a performance wall from a
   UDF that is heavily populated and
   frequently used, then that should be
   considered for inclusion in the
   master table.

3. Logical table design can take you to
   a certain point, but when the record
   counts get truly massive, you also
   should start looking at what table
   partitioning options are provided by your RDBMS of choice.

Design patterns for user defined fields with dropdownlist support

Are there any suggestions, and considerations I should make?

Yes. Start over, and let the DBMS do the work! That DataType column is a warning bell that something is wrong. The DBMS provides types, type safety, and type conversion.

Separate your UDFs into CustomIntFields, CustomStrFields, and CustomDateFields. If desired laster, you can represent them as a single view, using a UNION:

create view CustomFields as 
select 's' as type, FieldID, Name from CustomStrFields UNION
select 'i' as type, FieldID, Name from CustomIntFields UNION
select 'd' as type, FieldID, Name from CustomDateFields;

Just for starters, that will let the DBMS ensure on your behalf that dates have dates and integers have numbers.

The DropDowns table becomes

create table DropDowns
  ( DropDownID int  -- indicating the widget
  , type char(1) 
  , FieldID int
  );

referencing the union of the the three UDF tables.

This design lets fields be added without automatically appearing in the dropdown, which might not be what you want. If every field is supposed to appear in only one particular dropdown, the dropdown ID could be added to the three field tables and everything driven from the view.

What would be the most efficient way

This stuff is all very static and small. I have a hard time believing efficiency will be an issue. But I do think programmer and customer satisfaction will be higher by using the DBMS in the way it was intended. :-)

Implementing and indexing User Defined Fields in an SQL DB

It seems like you've listed your available options. EAV can be a pain for querying (and slow, depending on how many criteria you want to search on simultaneously), but it tends to be the most "sane" and RDBMS-agnostic implementation.

Modifying the schema is a no-no...obviously it can be done, but such a practice is abhorrent. I do not approve.

The XML option is a solution, and SQL Server can query inside the structure. I'm not certain about other RDBMS's, and you don't list which one you're using in the post or the tags.

If you're going to be querying on many attributes (say, 20+) simultaneously, then I would probably recommend the XML solution just to limit the number of joins you'll have to make. Aside from that, I would stick with EAV.

How would you create and store user-defined custom fields in a SQL database?

We add almost in our all application/products additional attribute/field support for given flexibility to user

Like we have a product category, In the category, customer can define additional attribute of any product

what we are doing in the DB level is:

Category Table have some additional column like: Text1Att, Text2Att...for text value support, Num1Att, Num2Att... for Number value support, Date1Att, Date2Att... for datetime value support, ID1Att, ID2Att... support for ID from other table like you can add dropdown, listbox,...

here all the column have String datatype.

what we store here is


we will store meta information here, like for Text1Att meta is

SSN;textbox;50;true;false;Null;

Caption of field;Control Type;Max length;is Required field;is Custom validation required; Custom Validation message;

birth place;textbox;100;true;true;Invalid Value;

Same for Numeric field ...

for date meta information will look like

birth date;Calendar control;true;true;Invalid Date;

Caption of field; Calendar control or can be other;is required;is Custom Validation; Custom Validation message;



What are doing in product table is add same number of column and have datatype text1Att,.. is varchar, num1Att have numeric, date1Att have datetime, ID1Att have int

What we are doing GUI side is : In category definition page add these attribute and build meta information at runtime and store in category table

On the other hand when we define product in category, meta information will be read and traverse from category table and populate in product definition page like other fields.

if u need further help, I can provide you images so that you will better understand how can be done this.

we are experience and analyze, this is much flexible approach

---

Related Topics