Question

Is it possible to return the row number as an ID?
In my view where i merge my tables I can’t make a unique ID because I need to create left
joins to store every value:

CREATE VIEW
sphinx
AS
SELECT

company.company_id,
company.company_name,
company.company_keywords,

company_address.address_street,
company_address.address_number,
company_address.address_telephone,
company_address.address_fax,
company_address.address_email,
company_address.address_website,
company_address.address_authorized,

company_contact.contact_name,
company_contact.contact_surname,
company_contact.contact_telephone,
company_contact.contact_mobilephone,
company_contact.contact_fax,
company_contact.contact_email,

company_page.page_content,
company_page.page_description,
company_page.page_keywords

FROM company
LEFT JOIN company_address ON company.company_id = company_address.company_id
LEFT JOIN company_page ON company.company_id = company_page.company_id
LEFT JOIN company_contact ON company.company_id = company_contact.company_id

When I receive the row number i can just do SELECT * FROM sphinx LIMIT 1 OFFSET rowNumber
to get the information of that row.

Thanks for your time.

Answer 1

You can do it the following way

SELECT * FROM
(
SELECT 
(@rownum:=@rownum + 1) as rownumber, q.*
FROM (
SELECT
* /*shortened for readability*/
FROM company
LEFT JOIN company_address ON company.company_id = company_address.company_id
LEFT JOIN company_page ON company.company_id = company_page.company_id
LEFT JOIN company_contact ON company.company_id = company_contact.company_id
, (select @rownum:=0) r
) q
) asdf
WHERE rownumber BETWEEN 2 AND 3 /*or whatever*/

EDIT: To explain a bit more:

This one

, (select @rownum:=0) r

declares and initializes the variable which will serve as our rownumber.
If you would include @rownum in the SELECT list of your inner most query, you would get a column which has the value 0 in each row.

So you make this inner query a subquery and just add 1 to the @rownum variable.
With only this

SELECT 
(@rownum:=@rownum + 1) as rownumber, q.*
FROM (
SELECT
* /*shortened for readability*/
FROM company
LEFT JOIN company_address ON company.company_id = company_address.company_id
LEFT JOIN company_page ON company.company_id = company_page.company_id
LEFT JOIN company_contact ON company.company_id = company_contact.company_id
, (select @rownum:=0) r
) q

you would already have a rownumber. Since you can’t refer to the column alias rownumber in the WHERE clause, you would have to write something like

WHERE (@rownum:=@rownum + 1) BETWEEN 2 AND 3 /*or whatever*/

but this would lead to false results, because the @rownum variable would get incremented again and your rownumber would be like

2
4
6

and so on. Therefore you have to put it in another subquery and then you can “limit” your query via the WHERE clause.

Any more questions?