通过 MySQL PHP 加入 3 表总和组

Question

I'm using Codeigniter, what I want to sum(stock_in) and sum(stock_out) and group by id_barang:

Table Stock

code	name	stock
B01	Book	40

Table Stock IN

code	name	stock in
B01	Book	20
B01	Book	10

Table Stock OUT

code	name	stock out
B01	Book	5
B01	Book	10

I want result: Summary

code	name	stock	stock in	stock out	last stock
B01	Book	40	30	15	55

last stock = (stock + stock in) - stock out

I can join 3 table but the sum(stock_in) and sum(stock_out) like this:

code	name	stock	stock in	stock out	last stock
B01	Book	40	60	30	70

Answer 1

As per your desired output INNER JOIN is used here. But If code (B01) is not exists in stock_in and Stock_out table then Use LEFT JOIN instead of INNER JOIN. COALESCE function is used in amount field to ignore NULL.

-- MySQL
SELECT s.code, s.name, s.stock, si.stock_in, so.stock_out
     , (s.stock + si.stock_in - so.stock_out) last_stock
FROM Stock s
INNER JOIN (SELECT code, MAX(name) name
                 , SUM(stock_in) stock_in
            FROM Stock_in
            GROUP BY code) si
        ON s.code = si.code
INNER JOIN (SELECT code, MAX(name) name
                 , SUM(stock_out) stock_out
            FROM Stock_out             
            GROUP BY code) so
            ON s.code = so.code;

Please check the result from url http://sqlfiddle.com/#!9/6dc765/4

Please check the result where left join is used http://sqlfiddle.com/#!9/9e97ef3/2

Answer 2

Here's one approach (using the fiddle thoughtfully provided by RahulBiswas) ...

SELECT s.code   
     , s.name
     , s.stock
     , SUM(CASE WHEN direction = 'in' THEN qty END) stock_in
     , SUM(CASE WHEN direction = 'out' THEN qty END) stock_out
     , s.stock+SUM(CASE WHEN direction = 'in' THEN qty END)-SUM(CASE WHEN direction = 'out' THEN qty END) balance
  FROM stock s
  JOIN 
     ( SELECT code
            , name
            , stock_in qty
            , 'in' direction
         FROM stock_in
        UNION ALL
       SELECT code
            , name
            , stock_out 
            , 'out' 
         FROM stock_out
    ) x
   ON x.code = s.code;
   

http://sqlfiddle.com/#!9/6dc765/10