SQL: Select AS with IF condition

Question

我有一个包含ITEM_ID, SELLER_ID, MSG_SENDER_ID and MSG_RECEIVER_ID列的MSG表，用于记录商品的买方和卖方之间的对话。

<表类> ITEM_ID SELLER_ID MSG_SENDER_ID MSG_RECEIVER_ID tbody><<tr>51125121

你在找这个吗?

SELECT *
,CASE 
WHEN SELLER_ID = MSG_SENDER_ID THEN 'buyer'
WHEN SELLER_ID = MSG_RECEIVER_ID THEN 'seller'
END AS type
FROM MSG