MySQL SELECT SUM based on another table

问题

I have an table on MySQL

tb_currencies

currencyid | currency_name
CU0001     | IDR
CU0002     | SGD
CU0003     | USD

tb_currency_converters

currencyconverterid | currency_month | from_currencyid_fk | to_currencyid_fk | amount
CC0001              | 2018-03-01     | CU0001             | CU0002           | 0.00009
CC0002              | 2018-03-01     | CU0002             | CU0001           | 10425
CC0003              | 2018-03-01     | CU0003             | CU0002           | 1.31964

tb_budgets

budgetid       | budget_month | departmentid_fk | currencyid_fk
BU201803000001 | 2018-03-01   | DP0003          | CU0002
BU201803000002 | 2018-03-01   | DP0002          | CU0002

tb_items

itemid | item_name | currencyid_fk | price
IT0001 | Mouse     | CU0001        | 165000
IT0002 | Keyboard  | CU0002        | 20
IT0003 | TV LCD    | CU0003        | 350

tb_pro_request

requestid      | budgetid_fk    | itemid_fk | quantity
RQ201803000001 | BU201803000001 | IT0002    | 1
RQ201803000002 | BU201803000001 | IT0003    | 5
RQ201803000003 | BU201803000001 | IT0004    | 1

Example:

My departmentid_fk is: DP0003, means I have Budget with Currency SGD.

On tb_pro_request, there are 2 items transaction different currency(IDR & USD) with Budget Department Currency(SGD).

What I want is, that 2 items with different currency need to convert first to SGD (Due to my Department Budget is: SGD) then SUM it.

*Logic, if the currency is SGD then no need to convert, but if not SGD then convert it first using tb_currency_converters then SUM it.

Is it possible to do in directly to query?

My query code so far:

SELECT
    R.requestid,
    R.budgetid_fk,
    R.category,
    R.itemid_fk,
    SUM(R.quantity),
    R.request_date,
    R.investmentid_fk,
    R.remarks,
    R.approval_status,
    I.itemid,
    I.item_name,
    I.price,
    SUM(R.quantity) * I.price as total, 
    B.budgetid,
    B.budget_month
FROM
    tb_pro_request R,
    tb_items I,
    tb_budgets B
WHERE
    R.itemid_fk = I.itemid AND
    R.budgetid_fk = B.budgetid AND
    R.investmentid_fk = '' AND
    B.active = 'Y' AND
    (R.approval_status = 'P' OR R.approval_status = 'A') AND
    DATE_FORMAT(B.budget_month,'%Y-%m') = '2018-03' AND
    B.departmentid_fk = 'DP0003'
    GROUP BY I.currencyid_fk

You can see there are 3 items with different currency below. What I want, convert to SGD for currency IDR, USD. then SUM it(to be 1 row)

回答1:

I think I mess up a bit in your FK, but at least you have the spirit ;)

SQL Fiddle

MySQL 5.6 Schema Setup:

Query 1:

SELECT
    R.budgetid_fk,
    SUM(R.quantity),
    SUM(R.quantity * I.price * COALESCE(CC.amount,1)) as total, 
    B.budgetid,
    B.budget_month
FROM tb_pro_request R 
INNER JOIN tb_items I 
  ON R.itemid_fk = I.itemid
INNER JOIN tb_budgets B 
  ON R.budgetid_fk = B.budgetid 
  AND B.active = 'Y'
LEFT JOIN tb_currency_converters CC 
  ON CC.from_currencyid_fk = I.currencyid_fk 
  AND CC.to_currencyid_fk = B.currencyid_fk
WHERE
    R.investmentid_fk = '' 
    AND (
      R.approval_status = 'P' 
      OR R.approval_status = 'A'
    ) 
    AND DATE_FORMAT(B.budget_month,'%Y-%m') = '2018-03' 
    AND B.departmentid_fk = 'DP0003'
GROUP BY R.budgetid_fk

Results:

|    budgetid_fk | SUM(R.quantity) |             total |       budgetid | budget_month |
|----------------|-----------------|-------------------|----------------|--------------|
| BU201803000001 |               7 | 575.2840143424692 | BU201803000001 |   2018-03-01 |

回答2:

Your query is invalid SQL, because you are aggregating the data and still show unaggregated columns, such as the requestid. Which requestid? There can be several.

The following groups by budget currency. If department_fk plus budget_month are unique in the table tb_budgets, then we are selecting just a single one and can hence remove the GROUP BY clause.

select
  sum(i.price * r.quantity * coaleasce(cc.amount, 1)) as total,
  c.currency_name
from tb_budgets b 
join tb_pro_request r on  r.budgetid_fk = b.budgetid 
                      and r.approval_status in ('P','A')
                      and r.investmentid_fk = ''
join tb_items i on i.itemid = r.itemid_fk
join tb_currencies c on c.currencyid = b.currencyid_fk
left join tb_currency_converters cc on  cc.currency_month     = b.budget_month
                                    and cc.from_currencyid_fk = i.currencyid_fk
                                    and cc.to_currencyid_fk   = b.currencyid_fk
where b.departmentid_fk = 'DP0003'
and date_format(b.budget_month,'%Y-%m') = '2018-03'
and b.active = 'Y'
group by c.currency_name;

来源：https://stackoverflow.com/questions/49104596/mysql-select-sum-based-on-another-table