Question

我尝试使用UNION加入以下SELECT语句，但最终我在同一列上获得了所有结果。但是，我希望每个查询的结果都在一个单独的列中。

SELECT Player_id,Game_id, R1
FROM poker_hands f, poker_cards a, poker_cards b
WHERE f.r1 = a.card_name 
AND f.r2 = b.card_name 
AND (f.hand_type = 'Four of kind' 
AND (a.game_value != b.game_value)
UNION ALL
/* R2 */
SELECT Player_id,Game_id, R2
FROM poker_hands f, poker_cards a, poker_cards b
WHERE f.r1 = a.card_name 
AND f.r2 = b.card_name 
AND (f.hand_type = 'High hand'
AND (a.game_value != b.game_value);

我希望输出类似

Player_id | Game_id | R1 | R2
0001      | 0002    |    | 8S
0002      | 0003    | 9H |
0003      | 0004    | 5C | 5S
0004      | 0005    |    | 6D

Answer 1

假设您的其余查询是正确的，请以这种方式使用它。第一次查询中null的硬编码R2和null的硬编码R1是第二次查询。

SELECT Player_id,Game_id, R1 , '' as R2
FROM poker_hands f, poker_cards a, poker_cards b
WHERE f.r1 = a.card_name 
AND f.r2 = b.card_name 
AND (f.hand_type = 'Four of kind' 
AND (a.game_value != b.game_value)
UNION ALL
/* R2 */
SELECT Player_id,Game_id, '' as R1, R2
FROM poker_hands f, poker_cards a, poker_cards b
WHERE f.r1 = a.card_name 
AND f.r2 = b.card_name 
AND (f.hand_type = 'High hand'
AND (a.game_value != b.game_value);

Answer 2

您可以使用case statement，请尝试以下操作：

SELECT Player_id,Game_id, CASE WHEN f.hand_type = 'Four of kind' THEN R1 ELSE '' END as R1,
CASE WHEN f.hand_type = 'High hand' THEN R2 ELSE '' END AS R2
FROM poker_hands f, poker_cards a, poker_cards b
WHERE f.r1 = a.card_name 
AND f.r2 = b.card_name 
AND (a.game_value != b.game_value AND (f.hand_type = 'High hand' OR f.hand_type = 'Four of kind' ));

MySQL加入多个SELECT查询

2 个答案: