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.
Note:
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:
Copy Code code as follows:
SELECT CONCAT (CAST (Int_col as CHAR), Char_col)
MySQL's concat function can connect one or more strings, such as
Copy Code code 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 ') |
+------------------------+
| 112233 |
+------------------------+
Row in Set (0.00 sec)
MySQL's concat function returns null if one of them is null when the string is concatenated
mysql> Select Concat (' One ', ' all ', null);
+------------------------+
| concat (' One ', ', ', null) |
+------------------------+
| NULL |
+------------------------+
Row in Set (0.00 sec)
