我如何 select 一个基于 mySQL 中另一列的列？

Question

以下脚本运行良好。但我想用一行而不是三行来写。 “尺寸”是从我的主程序传递过来的，它在这里用于测试。只是我想根据尺寸获得价格。

Table 列： LISTING_ID, PRICE_LARGE_PRICE, PRICE_SMALL_PRICE.

SET @Size = 'SMALL';

SELECT 
    PRICE_LARGE_PRICE,PRICE_SMALL_PRICE
INTO
    @PRICE_LARGE_PRICE,@PRICE_SMALL_PRICE
FROM
    prices
WHERE
    PRICE_LISTING_ID = 60;

SET @ITEM_PRICE = (CASE @Size WHEN 'REGULAR' THEN @PRICE_LARGE_PRICE 
WHEN 'SMALL' THEN @PRICE_SMALL_PRICE 
ELSE null 
END); 

SELECT @ITEM_PRICE;

感谢任何帮助。

Answer 1

我想你想要

SELECT 
  IF(@size == 'SMALL', PRICE_SMALL_PRICE, PRICE_LARGE_PRICE) AS ITEM_PRICE 
FROM prices;

Answer 2

以下可能有效。

SET @Size = 'SMALL';

SELECT 
    PRICE_LARGE_PRICE,
    PRICE_SMALL_PRICE, 
    CASE WHEN @Size = 'REGULAR' THEN PRICE_LARGE_PRICE
         WHEN @Size = 'SMALL' THEN PRICE_SMALL_PRICE
    END AS ITEM_PRICE 
INTO
    @PRICE_LARGE_PRICE,
    @PRICE_SMALL_PRICE, 
    @ITEM_PRICE 
FROM
    prices
WHERE
    PRICE_LISTING_ID = 60;

我如何 select 一个基于 mySQL 中另一列的列？

How could I select a column based on another column in mySQL?

mysql

select

case

case-when