Make selection from the results obtained from it

Question

Good afternoon,

I have the following table..

*eventos*
----------------------------------------
| id_evento | id_projeto | nome_evento |
----------------------------------------

I need to make a process as follows:

"Select events where the id_project is 1 with a limit of 2 records, but if the number of records is less than 2, select the last recorded events to complete the total number of 2 records."

Detailing... I need to select the records that have determined id_projeto but if by chance there is no record(with this id) I need to select the last two of the table events, and if by chance there is only 1, then I need to select only 1 more record.

I hope I’ve been clear. Any questions I answer.

Obs.: I am using mysql database

Answer 1

Use the ORDER BY FIELD next to the LIMIT to do this:

SELECT * FROM eventos ORDER BY FIELD(id_projeto, 1) DESC, id_evento DESC LIMIT 2

Answer 2

Considering the consultation by id_projeto = 1 can be done this way:

select 
id_evento,id_projeto,nome_evento, 1 as prioridade
from eventos where id_projeto =1

union

select 
id_evento,id_projeto,nome_evento, 2 as prioridade
from eventos where id_projeto !=1

order by prioridade, id_evento desc
limit 2;

I put in Sqlfiddle: http://sqlfiddle.com/#! 9/df682a/4