Question

是否可以将以下查询合并为单个，我基本上对获取上一个查询给出的结果感兴趣。

#This is wrong SQL only intended as pseudocode  

SELECT sum(amt) u FROM entry WHERE en_type='some_type' AND num='some_num';
SELECT sum(amt) v FROM entry WHERE en_type='some_other_type' AND num='some_num';
SELECT abal x FROM accounts WHERE num='the_same_num_as_above'; 
SELECT y = x + v - u;

Answer 1

使用子查询，您可以：

SELECT -(SELECT sum(amt) u FROM entry WHERE en_type='some_type' AND num='some_num')
       + (SELECT sum(amt) v FROM entry WHERE en_type='some_type' AND num='some_num')
       + (SELECT abal x FROM accounts WHERE num='the_same_num_as_above') AS y;

Answer 2

使用UNION制作合成的三行表，然后对其进行汇总。

SELECT SUM(x) y FROM
(
  SELECT sum(amt) AS x FROM entry WHERE en_type='some_type' AND num='some_num'
  UNION ALL
  SELECT sum(amt) AS x FROM entry WHERE en_type='some_type' AND num='some_num'
  UNION ALL
  SELECT -abal AS x FROM accounts WHERE num='the_same_num_as_above'
) A

我不确定我理解你的'the_same_num'内容，所以你需要解决这个问题。

结合数学查询MySQL

2 个答案: