连接单个表中的两列

Question

I am new to mysql.

This is my table structure

Test

id |   A    |B    |
1  |   11   |     |
2  |   12   |     |
3  |   13   |     |
4  |   14   |abc  |

I want to concatenate column A and column B and get output like below

id |   C   |
1  |   11  |
2  |   12  |
3  |   13  |
4  |   abc |

My question is,is it possible to get such output in mysql?

Answer 1

I think you are looking for the coalesce() function:

select id, coalesce(B, A) as C
from table t;

Answer 2

Use COALESCE() :

SELECT id, COALESCE (B, A) AS C
FROM yourtable

coalesce() evalutes arguments left->right, and returns the first non-null value.

Answer 3

尝试这个：

SELECT ID, IFNULL(B,A) AS C FROM Test