In order to create a table from another table with same schema, you can use the following command:
CREATE TABLE tablename_backup AS SELECT * FROM tablename;
If only certain columns of the original table are to be created as part of the new table, you can select column names within the create and select statement as follows:
CREATE TABLE tablename_backup(COL1, COL2, COL3) AS SELECT(COL1, COL2, COL3) FROM tablename;
If just the table schema of the tablename is required in the new backup table, use a select query run on tablename such that it returns no rows, e.g.
CREATE TABLE tablename_backup AS SELECT * FROM tablename WHERE id < 0;