Sql 使用EXTO的相关子查询

如何在

exto

中编写相关子查询

例如，SQL

SELECT

query的等价物是什么：

--Heaviest Lemmings per Group
SELECT ld.group_name, ld.id, ld.name, ld.weight
FROM lemming_data ld
WHERE weight = (
    SELECT max(weight)
    FROM lemming_data
    WHERE group = ld.group_name
);

---

在

exto

语法中？我不知道如何引用外部查询的

组名称

如果不使用片段，在Ecto中不可能使用共同相关的子查询。所以它会是这样的：

from ld in "lemming_data",
  where: ld.weight in fragment("(SELECT max(weight) FROM lemming_data WHERE group = ?)", ld.group_name),
  select: ld # or {ld.group_name, ld.id, ld.name, ld.weight}

或：

from ld in "lemming_data",
  where: fragment("? = (SELECT max(weight) FROM lemming_data WHERE group = ?)", ld.weight, ld.group_name),
  select: ld # or {ld.group_name, ld.id, ld.name, ld.weight}