Which is the best way to perform this query? Maybe UNION

Question

I have these four tables described bellow. Basically I have feeds with entries relationed with categories, and each category can be a main category or not (flag named as "principal"). Also each feed can be a partner feed or not (flag named as "parceiro").

I want to select all feed entries from partrners feeds, so I have this:

SELECT `e` . * , `f`.`titulo` AS `feedTitulo` , `f`.`url` AS `feedUrl`
FROM `feed_entries` AS `e`
INNER JOIN `feeds` AS `f` ON e.feed_id = f.id
INNER JOIN `entries_categorias` AS `ec` ON ec.entry_id = e.id
INNER JOIN `categorias` AS `c` ON ec.categoria_id = c.id
WHERE 
e.deleted =0
AND
f.parceiro =1
GROUP BY `e`.`id`
ORDER BY `e`.`date` DESC
LIMIT 5

Now I need to include in this result all entries from no partners feeds that are in main categories, I mean, only entries in main categories. So, the query bellow do this:

SELECT `e` . * , `f`.`titulo` AS `feedTitulo` , `f`.`url` AS `feedUrl`
FROM `feed_entries` AS `e`
INNER JOIN `feeds` AS `f` ON e.feed_id = f.id
INNER JOIN `entries_categorias` AS `ec` ON ec.entry_id = e.id
INNER JOIN `categorias` AS `c` ON ec.categoria_id = c.id
WHERE
e.deleted =0
AND 
c.principal =1
AND 
f.parceiro =0
GROUP BY `e`.`id`
ORDER BY `e`.`date` DESC
LIMIT 5

I need to merge these results in one query with limit 5 ordened by date.

Is UNION the best solution, if so, how to write the query?

CREATE TABLE categorias (
  id int(11) NOT NULL auto_increment,
  nome varchar(100) collate utf8_unicode_ci NOT NULL,
  principal int(1) NOT NULL default '0',
  PRIMARY KEY  (id),
  UNIQUE KEY nome (nome)
)

CREATE TABLE entries_categorias (
  id int(11) NOT NULL auto_increment,
  entry_id int(11) NOT NULL,
  categoria_id int(11) NOT NULL,
  PRIMARY KEY  (id),
  KEY entry_id (entry_id),
  KEY categoria_id (categoria_id)
)

CREATE TABLE feeds (
  id int(11) NOT NULL auto_increment,
  categoria_id int(11) NOT NULL,
  titulo varchar(255) collate utf8_unicode_ci NOT NULL,
  link varchar(255) collate utf8_unicode_ci NOT NULL,
  url varchar(255) collate utf8_unicode_ci NOT NULL,
  parceiro int(1) NOT NULL,
  PRIMARY KEY  (id),
  KEY categoria_id (categoria_id)
)

CREATE TABLE feed_entries (
  id int(11) NOT NULL auto_increment,
  feed_id int(11) NOT NULL COMMENT 'Testando os comentários',
  titulo varchar(255) collate utf8_unicode_ci NOT NULL,
  descricao text collate utf8_unicode_ci NOT NULL,
  slug varchar(255) collate utf8_unicode_ci NOT NULL,
  link varchar(255) collate utf8_unicode_ci NOT NULL,
  permaLink varchar(255) collate utf8_unicode_ci NOT NULL,
  html text collate utf8_unicode_ci NOT NULL,
  `date` datetime NOT NULL,
  created_at datetime NOT NULL,
  deleted int(1) NOT NULL,
  PRIMARY KEY  (id),
  UNIQUE KEY permaLink (permaLink),
  KEY feed_id (feed_id)
)

Answer 1

All that you should have to do is change the WHERE statement in the query:

SELECT `e`.*, `f`.`titulo` as `feedTitulo`, `f`.`url` as `feedUrl`

FROM `feed_entries` as `e`

INNER JOIN `feeds` as `f`
ON e.feed_id = f.id

INNER JOIN `entries_categorias` as `ec`
ON ec.entry_id = e.id

INNER JOIN `categorias` AS `c` 
ON ec.categoria_id=c.id

WHERE (e.deleted = 0 AND f.parceiro = 1) 
OR (e.deleted = 0 AND c.principal=1 AND f.parceiro = 0)

GROUP BY `e`.`id`
ORDER BY `e`.`date` desc
LIMIT 5

The new where statement has two conditions, so rather than querying the same set of tables/joins twice, we just query once and check both conditions!