An organic chemist in Michigan and a California sailboat captain have developed small-scale reactors that will transform hydrocarbon-based plastics back to their oily roots, reduce waste in landfills, divert plastics from entering oceans and cut down imported fuel costs for local communities.
Sunday, July 16, 2017
Saturday, February 25, 2017
1. To convert an existing integer column to auto-increment type 'serial' :
# Create a sequence called TABLE_id_seq (replace TABLE with actual table name). Find the maximum number and start the sequence with the next number. For example say max(id) is 30, then start with 31.
Command: create sequence TABLE_id_seq start with 31;
Anytime you can restart the sequence with 'restart with' option.
#Alter the table's column with default nextval function which will increment the integer when new rows are inserted into the table.
Command: alter table TABLE alter column COLUMN set default nextval('TABLE_id_seq');
2. To copy a table to a new one use commands:
create table NewTable as select * from OldTable;
alter table OldTable rename to Newname;
3. To rename a column:
alter table Table rename column Column to Newname