Return 列中具有完全相同项目的不同名称对

Question

我想在 table 中找到不同的名称对，它们在项目列中具有完全相同的项目。例如：

CREATE TABLE t
(
    name    VARCHAR(255),
    item    VARCHAR(255)
);

INSERT INTO t VALUES("Alice", "Orange");
INSERT INTO t VALUES("Alice", "Pear");
INSERT INTO t VALUES("Alice", "Lemon");
INSERT INTO t VALUES("Bob", "Orange");
INSERT INTO t VALUES("Bob", "Pear");
INSERT INTO t VALUES("Bob", "Lemon");
INSERT INTO t VALUES("Charlie", "Pear");
INSERT INTO t VALUES("Charlie", "Lemon");

这里的答案是 Alice,Bob 因为他们拿了完全相同的物品。

我只想用双重否定（使用 NOT EXISTS/NOT IN）来做，我认为这更适合这个问题，但我想不出任何接近的东西功能正常。

这有点类似于 this 问题 ~~但我使用的是 SQLite，所以我不能使用 GROUP_CONCAT()~~ 但我想知道它会怎样使用 NOT EXISTS/NOT IN.

使用关系除法完成

Answer 1

我可能已经找到解决您问题的方法。我的是使用 MySQL 测试的，但它没有使用 GROUP_CONCAT()。它可能适用于您的 SQLite 数据库。我的查询用于查找购买过相同商品的人。

尝试使用这个语句： SELECT DISTINCT e1.name, e2.name from t e1, t e2 WHERE e1.item=e2.item AND e1.name != e2.name GROUP BY e1.item HAVING count(*) >1;

https://gyazo.com/5e5e9d0ddfb33cb47439a674297108ed

Answer 2

这似乎适用于 SQLite

    select t1.name
    from t t1
        join t t2 on t1.name <> t2.name and t1.item = t2.item 
        join (select name, count(*) as cnt from t group by name) t3 on t3.name = t1.name
        join (select name, count(*) as cnt from t group by name) t4 on t4.name = t2.name
    group by t1.name, t3.cnt, t4.cnt
    having count(*) = max(t3.cnt, t4.cnt)

Answer 3

要获取所有名称对之间的共同项目数，您可以使用以下查询：

SELECT t1.name AS name1, t2.name AS name2, COUNT(*) AS cnt
FROM t AS t1
INNER JOIN t AS t2 ON t1.item = t2.item AND t1.name < t2.name
GROUP BY t1.name, t2.name

输出：

name1   name2       cnt
------------------------
Alice   Bob         3
Alice   Charlie     2
Bob     Charlie     2

现在您想要的只是过滤掉计数不等于 name1 和 name2 项数的 (name1, name2) 对。您可以使用带有相关子查询的 HAVING 子句来执行此操作：

SELECT t1.name AS name1, t2.name AS name2
FROM t AS t1
INNER JOIN t AS t2 ON t1.item = t2.item AND t1.name < t2.name
GROUP BY t1.name, t2.name
HAVING COUNT(*) = (SELECT COUNT(*) FROM t WHERE name = t1.name) AND 
       COUNT(*) = (SELECT COUNT(*) FROM t WHERE name = t2.name)

Demo here

Answer 4

与compound queries:

SELECT t1.name, t2.name
FROM t AS t1, t AS t2
GROUP BY t1.name, t2.name
HAVING t1.name < t2.name
   AND NOT EXISTS (SELECT item FROM t WHERE name = t1.name
                   EXCEPT
                   SELECT item FROM t WHERE name = t2.name)
   AND NOT EXISTS (SELECT item FROM t WHERE name = t2.name
                   EXCEPT
                   SELECT item FROM t WHERE name = t1.name);

可以使用 NOT IN，bit 表达完全相同的机制，但更复杂：

SELECT t1.name, t2.name
FROM t AS t1, t AS t2
GROUP BY t1.name, t2.name
HAVING t1.name < t2.name
   AND NOT EXISTS (SELECT item
                   FROM t
                   WHERE name = t1.name
                     AND item NOT IN (SELECT item
                                      FROM t
                                      WHERE name = t2.name))
   AND NOT EXISTS (SELECT item
                   FROM t
                   WHERE name = t2.name
                     AND item NOT IN (SELECT item
                                      FROM t
                                      WHERE name = t1.name));

Return 列中具有完全相同项目的不同名称对

Return distinct pairs of names which have the same exact items in column

sqlite

relational-division