mysql - 如何在一个查询中使 SQL 查询更干净、更好？

Question

我有这样的东西:

SELECT cars.brand, cars.id FROM cars WHERE cars.brand = 4 LIMIT 1;
SELECT cars.brand, cars.id FROM cars WHERE cars.brand = 24 LIMIT 1;
SELECT cars.brand, cars.id FROM cars WHERE cars.brand = 29 LIMIT 1;

如果有更多查询，它会很长。 如何以另一种方式，在一行中做到这一点？但对我来说重要的是速度。 cars.brand = X AND LIMIT X 是一个变量，因此它可能会改变。

Answer 1

您担心必须一一发送这么多查询，这样会花费很多时间。您可以改为进行以下一个查询:

SELECT cars.brand, cars.id FROM cars WHERE cars.brand = 4 LIMIT 1
UNION ALL
SELECT cars.brand, cars.id FROM cars WHERE cars.brand = 24 LIMIT 1
UNION ALL
SELECT cars.brand, cars.id FROM cars WHERE cars.brand = 29 LIMIT 1;