Question

Possible Duplicate:
how to change column datatype from character to numeric in postgresql 8.4

If I have a field of type varchar (and all the values are null or string representations of numbers) how do I use alter table to convert this column type to bigint?

Answer 1

To convert simply by parsing the string (casting):

alter table the_table alter column the_column type bigint using the_column::bigint

In fact, you can use any expression in terms of the_column instead of the_column::bigint to customise the conversion.

Note this will rewrite the table, locking out even readers until it’s done.