On Sat, May 24, 2014 at 11:53 PM, Smita <kumarismita62@gmail.com> wrote:


On Sat, May 24, 2014 at 10:25 PM, Marc Delisle <marc@infomarc.info> wrote:
Le 2014-05-24 12:16, Smita a écrit :
>
>
> On Sat, May 24, 2014 at 9:24 PM, Marc Delisle <marc@infomarc.info
> <mailto:marc@infomarc.info>> wrote:
>
>     Le 2014-05-24 11:03, Smita a écrit :
>     >
>     >
>     > On Sat, May 24, 2014 at 7:49 PM, Marc Delisle <marc@infomarc.info
>     <mailto:marc@infomarc.info>
>     > <mailto:marc@infomarc.info <mailto:marc@infomarc.info>>> wrote:
>     >
>     >     Hi Smita,
>     >     I have a doubt, looking at the structure you chose for this table:
>     >     db_name
>     >     column_list
>     >
>     >     This structure implies that, for any change, you have to load a
>     >     potentially big row, decode it and encode it. Imagine that
>     there are
>     >     hundreds or thousands of column definitions for this db.
>     >
>     >     I suggest something like:
>     >
>     >     db_name
>     >     column_name
>     >     column_attributes
>     >
>     > Yeah, agree. Thanks, It would be better to keep this. :-).
>     > I have a question: If we have "id interger(11) not null
>     auto_increment"
>     > already existing in central list, should we allow to add another
>     column
>     > "id integer(20) not null auto_increment" ? If we don't allow then
>     we can
>     > also keep structure like maybe:
>     > db_name
>     > column_name
>     > column_type
>     > column_collation
>     > column_isNull
>     > column_extra
>     >
>     > - Smita
>     >
>
>     In a central list, there should be only one column named "id" (but this
>     choice of name would be problematic, of course; a better choice would be
>     "customer_id").
>
> So We'll allow only unique column name. If same column name with
> different definition tried to add we just show the column name (with
> defination) already exist?

Yes; eventually I guess that in your project, there will be a way to
directly view the central list and change column definitions.

Yeah, I need to make a page to manage central columns, there users can view complete list of columns and edit some if they want.

>
>     Another example is "phone_number"; which is reused in the customer table
>     and in the salesperson table. You might want to always use CHAR(25) for
>     phone numbers.
>
>     So it's a good idea to split the attributes into separate columns like
>     in your example. The default value could be there too.
>
> Ok, thanks. We'll keep default as well.


Hi Marc,
I redesigned the database as discussed.  I completed the adding columns part but I got stuck when came to deletion. I have a question.
Let say I have two tables tbl1 and tbl2, both table has a common column name "phone_number". So If user selects both tables and asks to add unique columns to central list, then we are gonna add just one "phone_number" , let say we add the column/definition "phone_number" from tbl1. now let say user select tbl2 and ask to remove columns from central list. What should it do ? should it remove the column "phone_number" from central list or not ? as "phone_number" was added from tbl1.  but "phone_number" exists in tbl2 as well.

- Smita

--
Marc Delisle | phpMyAdmin

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