Re: [Babel] How to pass variables to SQL blocks?

From: "Sébastien Vauban" <wxhgmqzgwmuf-geNee64TY+gS+FvcfC7Uqw@public.gmane.org>
To: emacs-orgmode-mXXj517/zsQ@public.gmane.org
Subject: Re: [Babel] How to pass variables to SQL blocks?
Date: Wed, 01 Dec 2010 11:35:31 +0100	[thread overview]
Message-ID: <80tyixlr0s.fsf@missioncriticalit.com> (raw)
In-Reply-To: 87ipzefcga.fsf@gmail.com

Hi Eric,

"Eric Schulte" wrote:
> Sébastien Vauban <wxhgmqzgwmuf-geNee64TY+gS+FvcfC7Uqw@public.gmane.org> writes:
>
> Babel's sql support did not have any variable handling. I just copied over
> the variable support from ob-sqlite to ob-sql, so the following should now
> work (notice: my code block is different from yours)
>
> ** sql variables
> #+results: sql-param
> | table       | valueTable0       |
> | column      | valueColumn0      |
> | type        | valueType0        |
> | nullability | valueNullability0 |
>
> I want to apply the values onto the following chunk of code:
>
> #+srcname: add-column-in-table-0
> #+begin_src sql :var table=sql-param[0,1] :var column=sql-param[1,1] :var type=sql-param[2,1] :var nullability=sql-param[3,1]
> -- add column `@column' (if column does not exist yet)
> IF NOT EXISTS (SELECT *
>                FROM INFORMATION_SCHEMA.COLUMNS
>                WHERE TABLE_NAME = '@table'
>                AND COLUMN_NAME = '@column')
> BEGIN
>     ALTER TABLE $table
>     ADD $column $type @nullability
> END
> #+end_src
>
> results in the following code block expansion (C-c C-v v)
> #+begin_src sql
>   -- add column `@column' (if column does not exist yet)
>   IF NOT EXISTS (SELECT *
>                  FROM INFORMATION_SCHEMA.COLUMNS
>                  WHERE TABLE_NAME = '@table'
>                  AND COLUMN_NAME = '@column')
>   BEGIN
>       ALTER TABLE valueTable0
>       ADD valueColumn0 valueType0 @nullability
>   END
> #+end_src

For your information, this was the intended code snippet:

#+srcname: add-column-in-table-0
#+begin_src sql :var table=sql-param[0,1] :var column=sql-param[1,1] :var type=sql-param[2,1] :var nullability=sql-param[3,1] :tangle yes
-- add column `$column' (if column does not exist yet)
IF NOT EXISTS (SELECT *
               FROM INFORMATION_SCHEMA.COLUMNS
               WHERE TABLE_NAME = '$table'
               AND COLUMN_NAME = '$column')
BEGIN
    ALTER TABLE $table
    ADD $column $type $nullability
END
#+end_src

(I thought this feature would be implemented using "real" SQL vars, hence my @
prefix. But viewing the code shows the replacement is made outside of the SQL
snippet's knowledge.)

Tested. Works as expected... Thanks a lot!

Maybe the following should be put on some TODO list, even if not urgent?

>> * No warning if block does not exist
>>
>> Please note that inexistent references are ignored, without further notice.
>> That's the case for such a block (where I forgot the number suffix):
>>
>> #+srcname: contains-inexistent-ref
>> #+begin_src sql :noweb yes
>> <<add-column-in-table>>
>> #+end_src

Thanks.

Best regards,
  Seb

-- 
Sébastien Vauban

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