sql - 执行此查询的最佳方式是什么？也许是联盟

Question

我有下面描述的这四个表。基本上，我的提要包含与类别相关的条目，每个类别都可以是主类别，也可以不是主类别(标记名为“principal”)。此外，每个 Feed 都可以是合作伙伴 Feed，也可以不是(标记名为“parceiro”)。

我想从合作伙伴 feed 中选择所有 feed 条目，所以我有这个:

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

现在，我需要在此结果中包含来自主类别中的无合作伙伴提要的所有条目，我的意思是，仅包含主类别中的条目。因此，下面的查询执行此操作:

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

我需要将这些结果合并到一个查询中，限制为按日期排序 5。

UNION 是最好的解决方案吗？如果是，如何编写查询？

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

您所要做的就是更改查询中的 WHERE 语句:

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

新的 where 语句有两个条件，因此我们只需查询一次并检查两个条件，而不是查询同一组表/连接两次!