MYSQL中的SUM(子查询)

Question

基本上,我正在尝试以下方面:

SELECT m.col1, SUM(SELECT col5 FROM table WHERE col2 = m.col1)
FROM table AS m

这似乎不起作用.有什么解决方案吗？

Answer 1

你为什么不这样做:

SELECT m.col1, (SELECT SUM(col5) FROM table WHERE col2 = m.col1)
FROM table AS m

Answer 2

是 - 使用连接

SELECT m.col1, SUM(j.col5) FROM table AS m 
       JOIN table AS j ON j.col2 = m.col1 GROUP BY m.col1