How to merge two fields in mysql

Example: select (a + B) as c from table

Both types are varchar type, but the display is incorrect.

Until concat ()

Concat functions in MySQL

The following example describes how to use the concat function in MySQL, such as select concat ('11', '22', '33 ').

Concat functions in MySQL

Usage:

CONCAT (str1, str2 ,...)

Returns the string generated by the connection parameter. If any parameter is NULL, the return value is NULL.

Note:

If all parameters are non-binary strings, the result is a non-binary string.

If the independent variable contains any binary string, the result is a binary string.

A numeric parameter is converted to an equivalent binary string format. To avoid this, you can use an explicit cast type, for example:Copy codeThe Code is AS follows: select concat (CAST (int_col as char), char_col)

The concat function of MySQL can connect one or more strings, suchCopy codeThe Code is as follows: mysql> select concat ('10 ');
+ -------------- +
| Concat ('10') |
+ -------------- +
| 10 |
+ -------------- +
Row in set (0.00 sec)

Mysql> select concat ('11', '22', '33 ');
+ ------------------------ +
| Concat ('11', '22', '33') |
+ ------------------------ +
| 1, 112233 |
+ ------------------------ +
Row in set (0.00 sec)

When the concat function of MySQL connects to a string, if one of them is NULL, NULL is returned.
Mysql> select concat ('11', '22', null );
+ ------------------------ +
| Concat ('11', '22', null) |
+ ------------------------ +
| NULL |
+ ------------------------ +
Row in set (0.00 sec)