如何从表二中选择*并从表一中选择计数(t_type),其中表一和表二中的物种相等
表一 = 树
id | t_type
~~~~~~~~~~~~
1 | Tree one
2 | Tree two
3 | Tree Three
4 | Tree Four
5 | Tree one
表二 = 请求
id | req_species
~~~~~~~~~~~~
1 | Tree one
2 | Tree two
3 | Tree one
4 | Tree two
返回的表将具有与表二(请求)相同的行数,在本例中为 4 行。
预期输出
species | Qunatity
~~~~~~~~~~~~
Tree one | 2
Tree two | 1
Tree one | 2
Tree two | 1
最佳答案
一种方法使用相关子查询:
select r.species,
(select count(*) from trees t where t.species = r.species) as quantity
from requests r;
关于mysql - 选择 *FROM 表二并从表一计数(column_name),我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/38566427/