It is safe to say that, this table will have 100s of millions of records.
create table transactions ( trans_id number, -- unique values, primary key trans_description varchar2(500), trans_type varchar(20), -- highly skewed, highly used, need perfect histogram trans_comments varchar2(500), country varchar2(100), -- highly skewed, moderately used, need 'a' histogram insert_timestamp timestamp, update_timestamp timestamp, expire_timestamp timestamp )
It matter very very much and the fact that you have asked this question clearly indicates you shouldn't write a single line of DDL until you fully understand why. And you've not provided a single byte of information indicating the type of use this application and table will perform, whether single-instance or RAC, whether it will use replication, etc.
Lets say, there is a bitmap index on trans_type and btree index on country (does the type of index matter?!).
To delete histogram for a specific column you should use DBMB_STATS.DELETE_COLUMN_STATS
dbms_stats.gather_table_stats(<schema_name>, <table_name>, METHOD_OPT => FOR COLUMN SIZE <integer> <column_name>
col_stat_type => 'HISTOGRAM'