MYSQL UPDATE SELECT - 升级列

Question

BD Wordpress - 表：wp_term_relationships

object_id   |   term_taxonomy_id|   term_order
    1       |       23          |           0
    2       |       22          |           0
    3       |       23          |           0
    4       |       22          |           0
    5       |       23          |           0
    6       |       21          |           0

我需要计算有多少＆＃39;产品＆＃39;属于每个类别＆＃39;并插入列'term_order＆＃39;

例如：

object_id   |   term_taxonomy_id|   term_order
    1       |       23          |           3
    2       |       22          |           2
    3       |       23          |           3
    4       |       22          |           2
    5       |       23          |           3
    6       |       21          |           1

我做了类似的事情，但没有更新字段＆＃39; term_order＆＃39;：

UPDATE `letras`.`wp_term_relationships`
SET `term_order` = '2'
WHERE `wp_term_relationships`.`object_id` = '5' ;

SELECT  object_id as id_objeto, 
        COUNT(  `object_id` ) quantidade
FROM wp_term_relationships
WHERE `object_id` =  `object_id` 
GROUP BY  `term_taxonomy_id` 

Answer 1

您可以使用子查询将表连接到自身：

update t
set term_order = t2.cnt
from wp_term_relationships t
  join (
    select term_taxonomy_id, count(*) cnt
    from wp_term_relationships
    group by term_taxonomy_id
) t2 on t.term_taxonomy_id = t2.term_taxonomy_id;

• SQL Fiddle Demo

---

由于您使用的是MySQL，因此应该可以使用：

update wp_term_relationships 
  join (
    select term_taxonomy_id, count(*) cnt
    from wp_term_relationships
    group by term_taxonomy_id
) t2 on wp_term_relationships.term_taxonomy_id = t2.term_taxonomy_id
set wp_term_relationships.term_order = t2.cnt;

• Updated Fiddle

Answer 2

抱歉！

我在phpMyAdmin中执行：

update t
set term_order = t2.cnt
from wp_term_relationships t
  join (
    select term_taxonomy_id, count(*) cnt
    from wp_term_relationships
    group by term_taxonomy_id
) t2 on t.term_taxonomy_id = t2.term_taxonomy_id;

错误：

1064 - 您的SQL语法出错;查看与您的MySQL服务器版本对应的手册，以便在'wp_term_relationships t join'附近使用正确的语法（在第3行选择term_taxonomy_id，count（*）cn'