Problem creating a table with a subquery and a dblink

Question

Hello!!
I have a little problem. When I create a table with a subquery and a dblink, for example:
CREATE TABLE EXAMPLE2 AS SELECT * FROM EXAMPLE1@DBLINK
the table definition is changed. Fields with a type of CHAR or VARCHAR2 are created with a size three times bigger than the original table in the remote database. Field of type DATE and NUMBER are not changed. For example if the original table, in the database 1, has a field of type CHAR(1) it is create in the local database with a type of CHAR(3), and a VARCHAR2(5) field is created with VARCHAR2(15).
Database 1 has a WE8DEC character set.
Database 2 has a AL32UTF8 character set.
Could it be related to the difference in character sets?
What can I do to make Oracle use the same table definition when creating a table in this way?
Thanks!!

Answer 1

That is related to character sets, and probably necessary if you want all the data in the remote table to be able to fit in the new table.
When you declare a column VARCHAR2(5), by default, you're allocating 5 bytes of storage. In a single-byte character set, which I believe WE8DEC is, that also happens to equate to 5 characters. In a multi-byte character set like AL32UTF8, though, 1 character may require up to 3 bytes of storage, so you'd need to allocate 15 bytes to store that data. That's what's going on here.
You could still store all the data if you create the table locally by explicitly requesting 5 characters of storage by declaring the column VARCHAR2(5 CHAR). You could also set the NLS_LENGTH_SEMANTICS parameter to CHAR rather than BYTE before creating the table, but I believe that both of these will only apply when you're explicitly defining columns as part of your CREATE TABLE. I don't believe either will apply to CTAS statements.
Justin