MySQL bigint number - different output in SQL and R - mysql

Question

I have stored a value as varchar and as bigint in a MySQL DB:
userID_as_varchar varchar(50) DEFAULT NULL,
userID_as_bigint bigint(20) DEFAULT NULL,
+--------------------+---------------------------+
| userID_as_varchar | userID_as_bigint |
+--------------------+---------------------------+
| 917876131364446205 | 917876131364446200 |
+--------------------+---------------------------+
For any reason, I can't query the full userID_as_bigint value in full precision with SQL, but with R.
Behaviour SQL:
If I query the data or cast it it's always the "rounded" value.
Tested in phpMyAdmin and directly with sql command in shell.
Behaviour R:
If I query the field with R (RMySQL package) the value is complete 917876131364446205
Can anyone explain this behaviour or know a way how to get the full value with SQL.
Best regards.

Answer 1

Not quite sure what you mean, here's a test:
create table test(t1 varchar(50), t2 bigint);
Query OK, 0 rows affected (0.03 sec)
mysql> desc test
-> ;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| t1 | varchar(50) | YES | | NULL | |
| t2 | bigint(20) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.02 sec)
mysql> insert into test values('917876131364446205', 917876131364446205);
Query OK, 1 row affected (0.01 sec)
mysql> select * from test;
+--------------------+--------------------+
| t1 | t2 |
+--------------------+--------------------+
| 917876131364446205 | 917876131364446205 |
+--------------------+--------------------+
1 row in set (0.00 sec)