检查另一列中每行的值是否相同答案

【问题标题】：Check if values are the same for each row over a critiera in another column检查另一列中每行的值是否相同
【发布时间】：2021-12-30 10:47:24
【问题描述】：

DB-Fiddle

CREATE TABLE campaigns (
    id SERIAL PRIMARY KEY,
    campaign VARCHAR,
    supplier VARCHAR,
    plan_quantity DECIMAL
);

INSERT INTO campaigns
(campaign, supplier, plan_quantity)
VALUES 
('C001', 'supplier_a', '500'),
('C001', 'supplier_a', '500'),
('C001', 'supplier_b', '500'),

('C002', 'supplier_a', '600'),
('C002', 'supplier_b', '700'),

('C003', 'supplier_c', '100'),
('C003', 'supplier_c', '100'),

('C004', 'supplier_a', '900'),
('C004', 'supplier_c', '800'),
('C004', 'supplier_d', '250'),
('C004', 'supplier_d', '250');

预期结果：

campaign  |   supplier   |   plan_quantity   |     check      |
----------|--------------|-------------------|----------------|-------
  C001    |  supplier_a  |        500        |      same      |
  C001    |  supplier_a  |        500        |      same      |
  C001    |  supplier_b  |        500        |      same      |
----------|--------------|-------------------|----------------|-------
  C002    |  supplier_a  |        600        |    different   |
  C002    |  supplier_b  |        700        |    different   | 
----------|--------------|-------------------|----------------|-------
  C003    |  supplier_c  |        100        |      same      |
  C003    |  supplier_c  |        100        |      same      |
----------|--------------|-------------------|----------------|-------
  C004    |  supplier_a  |        900        |    different   |
  C004    |  supplier_c  |        800        |    different   |
  C004    |  supplier_d  |        250        |    different   |
  C004    |  supplier_d  |        250        |    different   |

在结果中的check 列中，我想查看每个supplier 和campaign 的plan_quantity 是否相同。
如果是，则应写为same，否则应写为different。

SELECT
campaign AS campaign,
supplier AS supplier,
plan_quantity AS plan_quantity,
(CASE WHEN plan_quantity for each supplier per campaign is the same THEN 'same' else 'different' END) AS check
FROM campaigns
ORDER BY 1,2,3;

我不知道我需要什么功能才能让它工作。
你有什么想法吗？

【问题讨论】：

标签： sql postgresql

【解决方案1】：

您可以使用窗口分析函数来检查值：

select *, 
  case when 
      Min(plan_quantity) over(partition by campaign) 
        = Max(plan_quantity) over(partition by campaign) 
    then 'same' else 'different'
    end as "Check"
from campaigns

【讨论】：

【解决方案2】：

您可以使用窗口max 和min

SELECT
  campaign AS campaign,
  supplier AS supplier,
  plan_quantity AS plan_quantity,
  CASE WHEN max(plan_quantity) over(partition by supplier, campaign) = min(plan_quantity) over(partition by supplier, campaign) THEN 'same' ELSE 'different' END AS check
FROM campaigns
ORDER BY 1,2,3;

【讨论】：

它在每一行都放置“相同”。
你的措辞模棱两可。尝试从partition 子句中删除supplier,

【解决方案3】：

您可以通过按campaign 分组来找出哪个campaign 具有唯一的plan_quantity，并简单地计算不同的plan_quantity

SELECT
    campaign AS campaign
FROM campaigns
GROUP BY campaign
HAVING COUNT(DISTINCT plan_quantity) = 1

这样你就可以做你想做的事了。以连接为例：

SELECT
    campaigns.campaign,
    supplier,
    plan_quantity,
    CASE WHEN grouping IS NOT NULL THEN 'same' ELSE 'different' END as check
FROM campaigns
    LEFT JOIN (
        -- Get all campaign with same plan_quantity
        SELECT
            campaign
        FROM campaigns
        GROUP BY campaign
        HAVING COUNT(DISTINCT plan_quantity) = 1
    ) as grouping
ON campaigns.campaign = grouping.campaign

【讨论】：