MySQL的选择

Question

增加新的专栏中，我有如下表

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

当我做出选择我要补充一个列。

例如

SELECT id,datenum, F1_baro_20_ FROM test 

而且我想增加一列，这样的事情：

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; 

这甚至有更复杂的表达式的作品，这样的：

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