比较两个查询结果并检查它们是否都存在值答案

【问题标题】：Compare two query results and check if value exist in both of them比较两个查询结果并检查它们是否都存在值
【发布时间】：2020-07-17 08:24:58
【问题描述】：

表格 (DB-Fiddle)

CREATE TABLE sales (
    id int auto_increment primary key,
    product VARCHAR(255),
    sales_date DATE,
    insert_time DATE
);

INSERT INTO sales
(product, sales_date, insert_time
)
VALUES 
("Product A", "2020-04-15", "2020-03-05"),
("Product B", "2020-05-20", "2020-03-05"),
("Product C", "2020-02-11", "2020-03-05"),

("Product A", "2020-04-15", "2020-03-06"),
("Product B", "2020-05-20", "2020-03-06"),
("Product C", "2020-02-11", "2020-03-06"),

("Product A", "2020-04-15", "2020-03-07"),
("Product B", "2020-05-20", "2020-03-07"),
("Product C", "2020-02-11", "2020-03-07");

在上面的表格中，每天都会插入产品销售额并分配给insert_time。

现在我想根据insert_time 检查此查询结果中的产品：

SELECT
product,
sales_date
FROM sales
WHERE insert_time = "2020-03-05";

也出现在这个查询的结果中：

SELECT
product,
sales_date
FROM sales
WHERE insert_time = "2020-03-05"
AND sales_date BETWEEN insert_time AND DATE_ADD(insert_time, INTERVAL 3 MONTH)

最终的结果应该是这样的：

product           sales_date         Check
Product A         2020-04-15         O.K.
Product B         2020-05-20         O.K.
Product C         2020-02-11         Error  (--> Because it only appears in the first query)

如何合并两个查询才能达到预期结果？

【问题讨论】：

试试INTERSECT

标签： mysql sql

【解决方案1】：

您可以使用 CASE 语句解决此问题：

SELECT
product,
sales_date,
    CASE
    WHEN sales_date BETWEEN insert_time AND DATE_ADD(insert_time, INTERVAL 3 MONTH) THEN 'Ok'
    ELSE 'Error' END AS 'Check'
FROM sales
WHERE insert_time = "2020-03-05";

您也可以使用 LEFT JOIN，但这意味着您必须敲击桌子两次：

SELECT all_records.product, all_records.sales_date, ifnull(filtered_records.Check, 'Error') AS `Check`
FROM
(
SELECT
product,
sales_date,
'Ok' AS 'Check'
FROM sales
WHERE insert_time = "2020-03-05"
) all_records
LEFT JOIN
(
SELECT
product,
sales_date,
'OK' AS 'Check'
FROM sales
WHERE insert_time = "2020-03-05"
AND sales_date BETWEEN insert_time AND DATE_ADD(insert_time, INTERVAL 3 MONTH)
) filtered_records
 ON all_records.product = filtered_records.product
 AND all_records.sales_date = filtered_records.sales_date

【讨论】：

【解决方案2】：

想到一个带有EXISTS 的CASE 表达式：

SELECT s.product, s.sales_date,
       (CASE WHEN EXISTS (SELECT 1
                          FROM sales s2
                          WHERE s2.product = s.product AND
                                s2.sales_date BETWEEN s2.insert_time AND DATE_ADD(s2.insert_time, INTERVAL 3 MONTH)
                         )
             THEN 'OK' ELSE 'ERROR'
        END) as flag
FROM sales s
WHERE s.insert_time = '2020-03-05';

请注意，check 是一个错误的列名称，因为它是一个 SQL 关键字（用于 check 约束）。

【讨论】：

dbfiddle.uk/…