01722. 00000 - "invalid number" : Oracle - sql

Question

I have a table1 with
t1id NUMBER(10,0)
channel_id NUMBER(10,0)
and another table2 with columns
t1id NUMBER(10,0)
channel2_id NVARCHAR2(100 CHAR)
cl2_id NVARCHAR2(100 CHAR)
Having called the query
SELECT t1.id, t2.cl2_id
FROM table1 t1
LEFT JOIN table2 t2
ON t1.channel_id = c.channel2_id;
I recieve the below error while joining the query.? Is it due to the data type of both the columns? how to resolve this
01722. 00000 - "invalid number"
*Cause: The specified number was invalid.
*Action: Specify a valid number.

Answer 1

If you have a datatype mismatch, we will (silently) try to correct that mismatch, eg
SQL> create table t ( num_col_stored_as_string varchar2(10));
Table created.
SQL>
SQL> insert into t values ('123');
1 row created.
SQL> insert into t values ('456');
1 row created.
SQL> insert into t values ('789');
1 row created.
SQL>
SQL> explain plan for
2 select * from t
3 where num_col_stored_as_string = 456;
Explained.
SQL>
SQL> select * from dbms_xplan.display();
PLAN_TABLE_OUTPUT
---------------------------------------------------------------------------
Plan hash value: 1601196873
--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 7 | 3 (0)| 00:00:01 |
|* 1 | TABLE ACCESS FULL| T | 1 | 7 | 3 (0)| 00:00:01 |
--------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter(TO_NUMBER("NUM_COL_STORED_AS_STRING")=456)
Notice that we silently added a TO_NUMBER to the filter to ensure that the column matched with the input value (456).
It then becomes obvious as to why this can cause problems, because:
SQL> insert into t values ('NOT A NUM');
1 row created.
SQL> select * from t
2 where num_col_stored_as_string = 456;
ERROR:
ORA-01722: invalid number
As others have suggested in comments, look at
getting your datatypes aligned
use TO_CHAR
use VALIDATE_CONVERSION
but ideally, data type alignment is the way to go