條件的MySQL柱

Question

表：qa_selltypes

selltype_code, selltype_name 
'1', 'unit' 
'2', 'pound' 
'3', 'box' 
'4', 'gallon' 

表：qa_items

item_code, item_name, selltype_code, item_price 
'1', 'PS2 Keyboard', '1', '10.45' 
'2', 'Screws', '3', '15.02' 
'3', 'Oil', '2', '30.00' 

我需要重新填充包含四個字段（單元，失速，磅，加侖）的網格，根據所述建立ITEM_PRICE與selltype_code字段的關係，其中一個示例：其餘的將它們設置爲0

DGV：

item_code, item_name, unit, box, pound, gallon 
'1', 'PS2 Keyboard', '10.45', '0', '0', '0' 
'2', 'Screws', '0', '0', '15.02', '0' 
'3', 'Oil', '0', '30.00', '0', '0' 

Answer 1

select i.item_code, i.item_name, 
    case when q.selltype_name = 'unit' then i.item_price else 0 end as unit, 
    case when q.selltype_name = 'box' then i.item_price else 0 end as box, 
    case when q.selltype_name = 'pound' then i.item_price else 0 end as pound, 
    case when q.selltype_name = 'gallon' then i.item_price else 0 end as gallon 
from qa_items i 
inner join qa_selltypes q on i.selltype_code = q.selltype_code 

Answer 2

您可以使用case。例如：

select case when some_column = 'abc' 
      then 'hello' 
      else 'good bye' 
      end as conditional_column 
from your_table