mysql - MySQL Left Join - 如何获取在第二个表中找到的记录数

Question

Table1

id    Name

1     John

2     Sheldon

3     Sarah

========

Table2

rid   id  id2  relation

1     1    2    1

2     1    3    1

如何在一个查询中从表 1 中获取所有成员以及每个成员的总关系。

我想要的结果应该是：

Jhon       2

Sheldon    0

Sarah      0

Answer 1

select Table1.name, count(Table2.id) from Table1 LEFT Join Table2 on Table1.id=Table2.id group by Table2.id

    OR 

select Table1.name,IFNULL(count(Table2.id), 0) from Table1  LEFT Join Table2  on Table1.id=Table2.id group by Table2.id

Answer 2

SELECT t1.name, IFNULL(COUNT(t2.id2), 0)
FROM table1 t1 LEFT JOIN table2 t2 ON t1.id=t2.id
GROUP BY t1.id