concat function Implementation database field merge query in MySQL

How do you merge two fields into a single field in MySQL? Tried a lot of ways, the result is still not what I want

For example: Select (A+b) as C from table

Types are also varchar type, but they are not displayed correctly.

Until Concat ()

concat function in MySQL

The following is an example of how to use the Concat function in MySQL, such as select Concat (' 11 ', ' 22 ', ' 33 ').

concat function in MySQL

How to use:

CONCAT (STR1,STR2,...)

Returns a string resulting from a connection parameter. If any of the arguments are null, the return value is null.

Attention:

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

If the argument contains any twos feed string, the result is a binary string.

A numeric parameter is converted to an equal binary string format; To avoid this, you can use explicit type cast, for example:

SELECT CONCAT (CAST (Int_col as CHAR), Char_col)
MySQL's concat function can connect one or more strings, such as

The code is as follows	Copy Code
Mysql> Select Concat (' 10 '); +--------------+ | Concat (' 10 ') | +--------------+ | 10 | +--------------+ 1 row in Set (0.00 sec) Mysql> Select concat (' 11 ', ' 22 ', ' 33 '); +------------------------+ | Concat (' 11 ', ' 22 ', ' 33 ') | +------------------------+ | 112233 | +------------------------+ 1 row in Set (0.00 sec)

The MySQL concat function returns null if one of the strings is null when the string is concatenated

The code is as follows	Copy Code
Mysql> Select Concat (' One ', ' all ', null); +------------------------+ | Concat (' One ', ', ', null) | +------------------------+ | NULL | +------------------------+ 1 row in Set (0.00 sec)

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