If a given value is stored into the CHAR(4) and VARCHAR(4) columns, the trailing spaces of values retrieved from the columns are removed from CHAR columns. : Char Varchar « Data Types « MySQL Tutorial

1. MySQL Tutorial
2. Data Types
3. Char Varchar

mysql>
mysql> CREATE TABLE myTable (v VARCHAR(4), c CHAR(4));
Query OK, 0 rows affected (0.01 sec)

mysql>
mysql> INSERT INTO myTable VALUES ('ab  ', 'ab  ');
Query OK, 1 row affected (0.00 sec)

mysql>
mysql> SELECT CONCAT('(', v, ')'), CONCAT('(', c, ')') FROM myTable;
+---------------------+---------------------+
| CONCAT('(', v, ')') | CONCAT('(', c, ')') |
+---------------------+---------------------+
| (ab  )              | (ab)                |
+---------------------+---------------------+
1 row in set (0.00 sec)

mysql>
mysql> drop table myTable;
Query OK, 0 rows affected (0.00 sec)

mysql>