SQL 仅显示包含这两项的结果

Question

我有一个 SQL table 上面有人们吃的名字和水果。我只希望结果显示同时吃苹果和香蕉的人的名字。但是如果我使用“Where Item='Banana' and item='Apple'，数据什么都不显示。如果我使用：Where item in('banana','apple')，它显示的结果如 table.

中所示

Name	Item
John	Apple
David	Banana
John	Banana

Answer 1

您可以使用 DISTINCT 和 EXISTS 子句来获得您需要的内容。

SELECT DISTINCT name
           FROM table1 a
          WHERE a.Item = 'Apple'
            AND EXISTS (SELECT *
                          FROM table1 b
                         WHERE b.Item = 'Banana'
                           AND b.Name = a.Name)

Answer 2

WITH CTE_Apple AS 
(
    SELECT * FROM Table where Item = 'Apple'
)
,
CTE_Banana AS 
(
    SELECT * FROM Table WHERE Item = 'Banana'

)
SELECT 
           A.Name 
FROM 
           CTE_Apple AS A
    JOIN
           CTE_Banana AS B ON B.Name = A.Name

基本上创建两个 sub-sets 数据并在数据相交的地方将它们连接在一起。还有很多其他方法可以做到这一点，但我发现 CTE（通用 Table 表达式）最优雅

Answer 3

使用子查询应该适用于任何 RDBMS：

select distinct Name 
from table_name
where Item = 'Apple'
and Name in 
(select Name from table_name where Item = 'Banana');

Answer 4

我们可以做一个 GROUP BY 然后 select 只吃列表中 2 个水果的人，即他们两个

CREATE TABLE eaten(
person VARCHAR (10),
fruit VARCHAR (10));

INSERT INTO eaten VALUES
('John','apple'),
('Bill','apple'),
('Bill','pear'),
('David','banana'),
('David','banana'),
('John','banana');

SELECT person
FROM eaten
WHERE fruit IN ('apple','banana')
GROUP BY person
HAVING COUNT(DISTINCT fruit) =2;

| person |
| :----- |
| John   |

db<>fiddle here

SQL 仅显示包含这两项的结果

SQL show only results that have both items

sql

relational-division