Mysql为选择添加新列

Question

我有下表

+-----+------------------+-------------+
| id  | datenum          | F1_baro_20_ |
+-----+------------------+-------------+
|   1 | 734152.000000000 |     1005.21 |
|   2 | 734152.006944445 |     1005.26 |
+-----+------------------+-------------+

当我做出选择时，我想再添加一列。

例如

SELECT id,datenum, F1_baro_20_ FROM test

我想添加一个列，如下所示：

SELECT id,datenum, F1_baro_20_, new_column=1 FROM test

+-----+------------------+-------------+------------+
| id  | datenum          | F1_baro_20_ |new_column  |
+-----+------------------+-------------+------------+
|   1 | 734152.000000000 |     1005.21 |       1    |
|   2 | 734152.006944445 |     1005.26 |       1    |
+-----+------------------+-------------+------------+

Answer 1

SELECT id, datenum, F1_baro_20_, 1 AS new_column FROM test;

这甚至适用于更复杂的表达式，如：

SELECT id, datenum, F1_baro_20_, (IF id = 2 THEN 1 ELSE 0) AS id_is_two FROM test;