Question

我有一张桌子;汽车

汽车有很多领域：颜色，品牌，型号，坠毁等等

我查询表格：

从颜色为红色的汽车中选择所有

然后，我想查询该结果，计算有多少已崩溃。（崩溃的字段是布尔值）

所以最后，我应该拥有的数据是红色汽车的所有字段，并且知道x已经崩溃了

是否可以在mysql门只敲一次？或者你必须做两个单独的查询？

感谢

Answer 1

一些数据：

mysql> select * from cars;
+-----+-------+---------+
| SNO | color | crashed |
+-----+-------+---------+
|   1 | red   |       0 |
|   2 | red   |       1 |
|   3 | red   |       1 |
|   4 | blue  |       1 |
|   5 | blue  |       1 |
|   6 | blue  |       1 |
|   7 | blue  |       0 |
+-----+-------+---------+

和查询：

mysql> select color,sum(crashed),count(*) as total from cars group by color;
+-------+--------------+-------+
| color | sum(crashed) | total |
+-------+--------------+-------+
| blue  |            3 |     4 |
| red   |            2 |     3 |
+-------+--------------+-------+
2 rows in set (0.00 sec)

Answer 2

您可以尝试：

SELECT * FROM cars WHERE color = "red" AND crashed = TRUE

或者无论你的崩溃指标是什么，我都只使用过SQL，但我相信此查询将显示所有红色车辆，并且崩溃值为true。

Answer 3

是的，你会使用WHERE条款。

SELECT * FROM cars WHERE Color = 'red' AND Crashed = true

或者如果你想按颜色崩溃，

SELECT color, count(*) FROM Cars WHERE crashed = true GROUP BY color;

或者，正如您澄清的那样，SELECT crashed, count(*) as yourval FROM Cars WHERE color = 'Red' GROUP BY crashed

mysql - count查询查询结果

3 个答案: