匹配来自不同表的两列 - MySQL PHP

Question

我在 mysql 中有两个表

• 表1是车辆，有所有车辆的记录
• 表2是贡献，记录了车辆的每日贡献

我在两个表中都有一个名为regno的列

我想要一个查询，该查询将显示不在contributions vehicle regno

我试过的：

SELECT vehicles.regno FROM vehicles,contributions
WHERE vehicles.regno<>contributions.regno
ORDER BY vehicles.regno;

请帮忙。 提前致谢。

Answer 1

尝试这个：

SELECT V.regno FROM vehicles AS V
LEFT JOIN contributions AS C
ON (V.regno = C.regno)
WHERE C.regno IS NULL;

Answer 2

您可以使用LEFT JOIN来获得结果：

SELECT v.regno
FROM vehicles v

LEFT JOIN contributions c ON c.regno = v.regno -- A LEFT JOIN produces a set of records which matches every entry in the left table (user) regardless of any matching entry in the right table

WHERE c.regno IS NULL -- This will filter out results where right table entry is not available
ORDER BY vehicles.regno;

Answer 3

SELECT regno FROM vehicles WHERE regno NOT IN (SELECT regno FROM contributions);