I have an Oracle table and a column (col1
) has type varchar2(12 byte)
. It has one row and value of col1
is 1234
W
Oracle says invalid number. Why is that? Why I cannot pass a number when it is varchar2?
Oracle does an implicit conversion from character type of col1
to number, since you're comparing it as a number.
Also, you assume that 1234
is the only row that's being fetched. In reality, Oracle has to fetch all rows from the table, and then filter out as per the where
clause. Now there's a character value in col1
that's being fetched before it encounters your 1234
row & that's causing the error, since the character cannot be converted to a number.
This fiddle shows the behaviour. Since abc
canot be converted to a number, you get that error message
Now if the only record in the table is that of col1 containing a numeric character, you'll see that the statement will work fine
Oh, it is much better to convert to char rather than to numbers:
select *
from table
where col1 = to_char(1234)
When the col1 does not look like a number, to_number returns an error, stopping the query.
The problem is that you expect that Oracle will implicitly cast 1234 to a character type. To the contrary, Oracle is implicitly casting the column to a number. There is a non-numeric value in the column, so Oracle throws an error. The Oracle documentation warns against implicit casts just before it explains how they will be resolved. The rule which explains the behaviour you're seeing is:
When comparing a character value with a numeric value, Oracle converts the character data to a numeric value.