使用 SQL，如何从父子关系的两列中找到表中的子编号？
[英]Using SQL, how do you find the child number in a table from two columns where they are parent-child relationships?
问题描述
From this table, after querying I want to get the child column that shows the number of the child for each id.
从此表中，查询后我想获取显示每个 id 的子编号的子列。
I want:我想：
1 个解决方案
解决方案1
0 2022-09-18 13:17:10
A scalar subquery will produce the data you want.标量子查询将产生您想要的数据。 For example:例如：
select
t.*,
(select count(*) from t b where b.parent_id = t.id) as child
from t
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