Can I pass a number for varchar2 in Oracle?

Question

I have an Oracle table and a column (col1) has type varchar2(12 byte). It has one row and value of col1 is 1234

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Answer 1

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.