mysql - 使用从计算另一个表中提取的值更新 mysql 行

Question

我有以下查询：

SELECT int_intrebari.id, COUNT( id_raspuns ) AS nr_raspunsuri
FROM int_intrebari, int_raspunsuri
WHERE int_intrebari.id = int_raspunsuri.id
GROUP BY id

是否可以使用查询中的 nr_raspunsuri 更新第一个表，而无需编写 foreach 语句？

Answer 1

你可以UPDATE这样JOIN：

UPDATE int_intrebari i1
INNER JOIN
(
    SELECT id, COUNT( id_raspuns ) AS nr_raspunsuri
    FROM int_intrebari
    GROUP BY id 
) i2 ON i1.id = i2.id
SET i1.nr_raspunsuri = i2.nr_raspunsuri

Answer 2

你可以这样做 -

update int_intrebari left join int_raspunsuri on int_intrebari.id =int_raspunsuri.id
set int_intrebari.column_to_update = int_raspunsuri.column_from_update_second_table

Answer 3

UPDATE
  (SELECT int_intrebari.id, COUNT( id_raspuns) AS nr_raspunsuri
   FROM int_intrebari, int_raspunsuri
   WHERE int_intrebari.id = int_raspunsuri.id
   GROUP BY id) t1,
  int_raspunsuri t2
SET
  t2.nr_raspunsuri=t1.nr_raspunsuri
WHERE
  t1.id=t2.id