Question

SQL小提琴here

"id"    "type"  "parent"    "country"   "totals"
1       3       0           US          0       //Desired output 5
2       10      1           US          0
3       10      1           US          0
4       10      1           US          0
5       10      1           US          0
6       10      1           US          0

7       3       0           US          0       //Desired output 5
8       10      7           US          0
9       10      7           US          0
10      10      7           US          0
11      10      7           US          0
12      10      7           US          0

13      3       0           SE          0       //Desired output 1
14      10      13          SE          0

15      3       0           SE          0       //Desired output 3
16      10      15          SE          0
17      10      15          SE          0
18      10      15          SE          0

在上表中，我正在尝试使用其子项(how many children a parent has. I'll supply the parent id and country)更新父级。

父母是type 3，孩子是type 10，国家代码在旁边。

我要做的是：

$parent = 10;
$country = 'US';

`select count(*) as totalChildren, parent, country where type= 10 and parent = $parent and country = $country` then
`update table set totals = totalChildren where parent = parent from above and country = country from above`.

我目前使用下面的SQL来更新整个表，但是如果我只需要更新一个特定的父级，我应该把where子句放在下面的sql中。我对此感到困惑。

UPDATE  likesd a // where parent = $parent and country = $country - where should this go?
        INNER JOIN
        (
            SELECT  country, parent, count(id) totalChildren
            FROM    likesd
            WHERE   type = 10
            GROUP   BY parent
        ) b ON a.id=b.parent and a.country = b.country
SET     a.totals = b.totalChildren
WHERE   a.type = 3 and a.id = b.parent and a.country = b.country;

Answer 1

由于你只有一个孩子与父母的关系，这应该有效：

UPDATE likesd l
JOIN (
  SELECT COUNT(1) cnt, parent
  FROM likesd 
  WHERE parent = ?
  GROUP BY parent
  ) l2 ON l.id = l2.parent
SET l.totals = l2.cnt

Update Fiddle Demo

我假设ID是您的主键，因此无需提供国家/地区。但是，如果确实需要，请将其放在子查询中的WHERE子句中。

where子句在哪里进入这个sql？

1 个答案: