[英]Combine records from differing tables using JOIN and UNION
我需要创建一个查询来组合来自两个表的数据,我想可能是JOIN和UNION的组合。
在这个例子中,我需要列出状态为活动状态的所有名称,只需一次,将他们的葡萄酒,苏打水,晚餐,甜点和水果首选项组合在一起,按名称排序。
我不确定JOIN是否会起作用,因为名称并不总是在两个表中,并且UNION很棘手,因为它们没有相同的列。 我已经尝试使用空值来使UNION工作,但是这给了我每个名称的重复行,而不是将它们分组为每个名称一行。
DRINK
====================================
name status wine soda
---------- ------ ------ ------
John Smith active red cola
Mary Jones active white lemonade
Tom Brown old red fanta
Judy White active red dr pepper
Sam Wing old red cola
FOOD
=============================================
name status dinner dessert fruit
---------- ------ ------ ------ ------
John Smith active steak muffin apple
Mary Jones active fish cake kiwi
Walter Yu active pasta cake banana
Jim Adams old steak candy apple
Adam Sheers active pasta candy grapes
我需要查询来生成这样的结果 -
RESULT
==================================================================
name status wine soda dinner dessert fruit
---------- ------ ------ ------ ------ ------ ------
Adam Sheers active - - pasta candy grapes
John Smith active red cola steak muffin apple
Judy White active red dr pepper - - -
Mary Jones active white lemonade fish cake kiwi
Walter Yu active - - pasta cake banana
非常感谢您对此的任何帮助!
这应该工作:
SELECT names.name, drink.wine, drink.soda, food.dinner, food.dessert, food.fruit
FROM
(SELECT name FROM food WHERE status = 'active'
UNION
SELECT name FROM drink WHERE status = 'active') names
LEFT JOIN drink ON drink.name = names.name
LEFT JOIN food ON food.name = names.name
结果
| NAME | WINE | SODA | DINNER | DESSERT | FRUIT | ---------------------------------------------------------------- | John Smith | red | cola | steak | muffin | apple | | Mary Jones | white | lemonade | fish | cake | kiwi | | Walter Yu | (null) | (null) | pasta | cake | banana | | Adam Sheers | (null) | (null) | pasta | candy | grapes | | Judy White | red | dr pepper | (null) | (null) | (null) |
SELECT name, status, MAX(wine) wine, MAX(soda) soda, MAX(dinner) dinner, MAX(dessert) dessert, MAX(fruit) fruit
FROM
(
SELECT name, status, wine, soda, NULL dinner, NULL dessert, NULL fruit
FROM DRINK WHERE status = 'active'
UNION ALL
SELECT name, status, NULL wine, NULL soda, dinner, dessert, fruit
FROM FOOD WHERE status = 'active'
) R
GROUP BY name, status
select *
from food f
left join drink d on f.name = d.name
where d.status = 'active' and f.status = 'active'
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