MySQL选择ID匹配的另一个表的行数

Question

我试图从一个表中选择另一个表的计数，其中 id 与原始 tableID 匹配，类似于：

select *, (count(0) from table2 where table2.table1ID = table1.table1ID) count
    from table1

这个的 mySQL 语法是什么？

Answer 1

select
  table1.*,
  if(table2.table1ID is null,0,count(*))
from
  table1
  left join table2 on table1.table1ID = table2.table1ID
group by
  table1.table1ID;

Answer 2

SELECT COUNT(b.*) FROM table1 as a
LEFT JOIN table2 as b ON a.tableID = b.tableID