UPDATE coolTable SET columnA = columnB;

CREATE TABLE pweb (_id INTEGER PRIMARY KEY,h_id  INTEGER ,sent  INTEGER);

sqlite> select * from pweb;
1|10|1
2|20|1
3|30|0
4|40|0

sqlite> update pweb set h_id = _id;

sqlite> select * from pweb;
1|1|1
2|2|1
3|3|0
4|4|0