Question

好吧所以标题有点乱，但我有一张city这样的表：

id | name     | population
1  | Bla bla  | 1323
2  | Blaer    | 35365

现在我从另一张桌子中选择一张桌子：

INSERT INTO tmp (
    name, age, city_id
)
SELECT
    NAME,
    AGE,
    CITY
FROM main;

问题是SELECT CITY，因为CITY是城市的名称，但我需要id。所以基本上我想要这样的东西，但这不起作用：

INSERT INTO tmp (
    name, age, city_id
)
SELECT
    NAME,
    AGE,
    city.id FROM city WHERE city.name = CITY
FROM main;

Answer 1

使用city表执行INSERT INTO tmp ( name, age, city_id ) SELECT NAME, AGE, c.id FROM main m INNER JOIN city c on m.city=c.name ;并在select子句中使用它。

adapter.getCount() == 0

Answer 2

从价值中找到id有点不寻常。为什么要在主表中存储城市？你应该在那里存储城市ID。

但是简单的JOIN会做：</ p>

INSERT INTO tmp (name, age, city_id)
SELECT
    m.NAME,
    m.AGE,
    c.id
FROM main m join city c on m.city = c.name

Answer 3

试试这个

INSERT INTO tmp(
  name,
  age,
  city_id
)
SELECT 
  m.name AS name,
  m.age AS age,
  (SELECT c.id FROM city c WHERE c.name = m.city) AS city_id
FROM main m

根据另一个表的值从另一个表中选择一列

3 个答案: