mysql - 如何通过在MySQL中的另一个表中创建行来选择表中的列

Question

我有三个表。

• 税务主管
• item_master
• item_tax

里面的值是这样的

*tax_master*
tax_id  tax_name tax_value
--------------------------
  1     Vat      5
  2     LBT      8

*item_master*
item_id   Prise
---------------
  1        30
  2        100

*item_tax*
item_tax_id   item_id   tax_id
------------------------------
    1           1         1
    2           2         2
    3           1         2

现在我想要这样的输出。

item_id  prise VAT   LBT   Total_prise
---------------------------------------
   1      30   1.5   2.4      33.9
   2     100    -     8       108

增值税值的计算方式为 5/30*100，如 5% on 30=1.5

Answer 1

select item_id, price,
       (min(case when tax_name = 'VAT' then tax end)) vat,
       (min(case when tax_name = 'LBT' then tax end)) lbt,
       coalesce(min(case when tax_name = 'VAT' then tax end),0) +
       coalesce(min(case when tax_name = 'LBT' then tax end),0) +
       price total
  from 
      (select a.item_id item_id,
              c.tax_name tax_name,
              (c.tax_value * b.price / 100) tax,
              b.price price
         from item_tax a inner join item_master b on a.item_id = b.item_id
                         inner join tax_master c on a.tax_id = c.tax_id) as calc
 group by item_id, price;

演示 here .