Question

我有两张表，记录和数据。记录有多个字段（名字，姓氏等）。这些字段中的每一个都是存储实际值的数据表的外键。我需要搜索多个记录字段。

以下是使用INTERSECT的示例查询，但我需要一个在MySQL中运行的查询。

SELECT records.id FROM records, data WHERE data.id = records.firstname AND data.value = "john"
INTERSECT
SELECT records.id FROM records, data WHERE data.id = records.lastname AND data.value = "smith"

感谢您的帮助。

Answer 1

您可以使用内部联接来筛选在另一个表中具有匹配行的行：

SELECT DISTINCT records.id 
FROM records
INNER JOIN data d1 on d1.id = records.firstname AND data.value = "john"
INNER JOIN data d2 on d2.id = records.lastname AND data.value = "smith"

许多其他选择之一是in子句：

SELECT DISTINCT records.id 
FROM records
WHERE records.firstname IN (
    select id from data where value = 'john'
) AND records.lastname IN (
    select id from data where value = 'smith'
)

Answer 2

我认为这种方法更容易理解，但由于您最初加载了大量重复记录，因此会产生一些开销。我在具有大约10000-50000条记录的数据库上使用它，并且通常相交大约5个查询，并且性能可以接受。

您要做的只是“UNION ALL”每个要交叉的查询，并查看每次都有哪些查询。

SELECT * From (

    (Select data1.* From data1 Inner Join data2 on data1.id=data2.id where data2.something=true)
    Union All
    (Select data1.* From data1 Inner Join data3 on data1.id=data3.id where data3.something=false)

) As tbl GROUP BY tbl.ID HAVING COUNT(*)=2

因此，如果我们在两个查询中都获得相同的记录，那么它的计数将为2，最终的环绕查询将包含它。

Answer 3

改为使用联接：

SELECT records.id
FROM records
JOIN data AS D1 ON records.firstname = D1.id
JOIN data AS D2 ON records.lastname = D2.id
WHERE D1.value = 'john' and D2.value = 'smith'

以下是一些测试数据：

CREATE TABLE records (id INT NOT NULL, firstname INT NOT NULL, lastname INT NOT NULL);
INSERT INTO records (id, firstname, lastname) VALUES
(1, 1, 1),
(2, 1, 2),
(3, 2, 1),
(4, 2, 2);

CREATE TABLE data (id INT NOT NULL, value NVARCHAR(100) NOT NULL);
INSERT INTO data (id, value) VALUES
(1, 'john'),
(2, 'smith');

预期结果：

测试数据可能对海报没有用，但对于想要检查解决方案以确定其工作正常的选民，或者想要提交答案以便他们可以测试自己答案的人来说，可能会有用。

Answer 4

MYSQL中INTERSECT的一般替代是内连接：

SELECT DISTINCT * FROM 
(SELECT f1, f2, f3... FROM table1 WHERE f1>0)
INNER JOIN
(SELECT f1, f2, f3... FROM table2 WHERE f1>0)
USING(primary_key)

或者特别针对您的情况：

SELECT DISTINCT * FROM 
(SELECT records.id FROM records, data WHERE data.id = records.firstname AND data.value = "john") query1
INNER JOIN
(SELECT records.id FROM records, data WHERE data.id = records.lastname AND data.value = "smith") query2
USING (id)

Answer 5

SELECT t.id FROM table t WHERE NOT EXISTS (SELECT t2.id, FROM table2 t2 WHERE t2.id = t1.id)

https://dev.mysql.com/doc/refman/5.7/en/exists-and-not-exists-subqueries.html

Answer 6

由于Mysql不支持INTERSECT，因此您可能有两种选择：内部联接和 in 。这是 in 中的解决方案：

SELECT records.id FROM records, data 
WHERE data.id = records.firstname AND data.value = "john"
    AND records.id in (SELECT records.id FROM records, data 
    WHERE data.id = records.lastname AND data.value = "smith);

Answer 7

我参加聚会有点晚了，但是我认为完全模仿INTERSECT的最干净，最好的方法是：

SELECT * FROM
( SELECT records.id FROM records, data WHERE data.id = records.firstname AND data.value = "john" ) x1
NATURAL JOIN
( SELECT records.id FROM records, data WHERE data.id = records.lastname AND data.value = "smith" ) x2

MySQL中的INTERSECT

7 个答案: