MySQL - 将字段连接到附加字段

Question

简单的一个真的 - 或者应该是。

我有多个字段要压缩并附加到一个长文本字段。

我猜这是一个 concat 函数，但我不知道如何将连接的值附加到具有现有值的同一行中的字段。

是否有一个 MySQL 语句可以解决问题，还是我必须运行一个循环的 php 脚本？

示例...

ID | NAME | POSITION | NOTES
1 | Richard | Programmer | Not paid enough
2 | David | Manager | Lazy
3 | Hilary | Personnel Manager | Doesn't care

最终，我想删除 NAME 和 POSITION 字段，但我想预先存储这些值，因此我想连接“-”.NAME。”-“.POSITION 并将其附加到 NOTES 中而不会丢失该字段中的任何数据所以结果是……

ID | NAME | POSITION | NOTES
1 | Richard | Programmer | Not paid enough - Richard - Programmer
2 | David | Manager | Lazy - David - Manager
3 | Hilary | Personnel Manager | Doesn't care - Hilary - Personnel Manager

这有意义吗？

Answer 1

CONCAT 函数可以在 MySQL 中轻松处理：

SELECT
    ID,
    NAME,
    POSITION,
    CONCAT(NOTES, ' - ', NAME, ' - ', POSITION) AS NOTES
FROM yourTable;

Answer 2

drop table if exists t;
create table t(ID int, NAME varchar(20), POSition varchar(20),NOTES varchar(500));
insert into t values
(1 , 'Richard' , 'Programmer' ,      'Not paid enough'),
(2 , 'David'   , 'Manager'    ,      'Lazy'),
(3 , 'Hilary'  , 'Personnel Manager','Doesnt care');

update t
set notes =
    CONCAT(NOTES, ' - ', NAME, ' - ', POSITION) 
where 1 = 1;

select * from t;

+------+---------+-------------------+------------------------------------------+
| ID   | NAME    | POSition          | NOTES                                    |
+------+---------+-------------------+------------------------------------------+
|    1 | Richard | Programmer        | Not paid enough - Richard - Programmer   |
|    2 | David   | Manager           | Lazy - David - Manager                   |
|    3 | Hilary  | Personnel Manager | Doesnt care - Hilary - Personnel Manager |
+------+---------+-------------------+------------------------------------------+
3 rows in set (0.00 sec)

最后，我想删除 NAME 和 POSITION 字段你确定要这样做吗？再次取出碎片是一种痛苦。

如果任何元素为空，如果不能保证元素有值，则 concat 将返回 null，则需要进行 ifnull 测试

    update t
    set notes =
        CONCAT(IFNULL(NOTES,''), ' - ', IFNULL(NAME,''), ' - ', IFNULL(POSITION,'')) 
    where 1 = 1;

drop table if exists t;
create table t(ID int, NAME varchar(20), POSition varchar(20),NOTES varchar(500));
insert into t values
(1 , 'Richard' , 'Programmer' ,      'Not paid enough'),
(2 , 'David'   , 'Manager'    ,      'Lazy'),
(3 , 'Hilary'  , 'Personnel Manager','Doesnt care'),
(4 , 'HILARY'  , NULL,'DOES NOW') ;

update t
set notes =
    CONCAT(IFNULL(NOTES,''), ' - ', IFNULL(NAME,''), ' - ', IFNULL(POSITION,'')) 
where 1 = 1;

+------+---------+-------------------+------------------------------------------+
| ID   | NAME    | POSition          | NOTES                                    |
+------+---------+-------------------+------------------------------------------+
|    1 | Richard | Programmer        | Not paid enough - Richard - Programmer   |
|    2 | David   | Manager           | Lazy - David - Manager                   |
|    3 | Hilary  | Personnel Manager | Doesnt care - Hilary - Personnel Manager |
|    4 | HILARY  | NULL              | DOES NOW - HILARY -                      |
+------+---------+-------------------+------------------------------------------+
4 rows in set (0.00 sec)