Question

我有一张桌子：

OC  Period(MM/YYYY) Ing
CHO 04/01/2016      100
CHO 04/01/2016      200
CHO 04/01/2016      0
CFE 04/01/2016      400
CFE 04/01/2016      350
CFE 04/01/2016      0

我有一个像这样的SQL查询：

  (SELECT OC,Ing FROM contacts c where ing > 0)
  UNION ALL
  (SELECT OC,Sum(Ing) FROM contacts c where ing = 0 Group by OC)

我想得到这样的结果：

Ref Period(MM/YYYY) Ing
CHO 04/01/2016      100
CHO 04/01/2016      200
CHO 04/01/2016      300
CFE 04/01/2016      400
CFE 04/01/2016      350
CFE 04/01/2016      750

Answer 1

int var = 2;
cout << "var' address and value: " << &var << " " << var << endl;
cout << (int*)(&var) << endl;
cout << *(int*)(&var) << endl;
cout << (int*)*(int*)(&var) << endl;


int *ptr = &var;
cout << "ptr's address： " << &ptr << endl;
cout << (int*)(&ptr) << endl;
cout << *(int*)(&ptr) << endl;//NOT var's address, WHY?
cout << (int*)*(int*)(&ptr) << endl; //var's address,
cout << *(int*)*(int*)(&ptr) << endl; //var's value,

如果需要对输出进行排序

，可以将其包装在另一个

(SELECT c.OC, c.Period, c.Ing FROM contacts c where c.ing > 0)
UNION ALL
(SELECT c.OC, c.Period, Sum(c.Ing) AS Ing FROM contacts c Group by c.OC, c.Period)

语句中

如何在同一个表上使用union查询和mysql中的sum（value）？

1 个答案: