ALTER TABLE ADD COLUMN takes a long time

Question

I was just trying to add a column called \"location\" to a table (main_table) in a database. The command I run was

ALTER TABLE main_table ADD COLUMN location         


        

Answer 1

Alter table takes a long time with a big data like in your case, so avoid to use it in such situations, and use some code like this one:

select main_table.*, 
  cast(null as varchar(256)) as null_location, -- any column you want accepts null
  cast('' as varchar(256)) as not_null_location, --any column doesn't accept null
  cast(0 as int) as not_null_int, -- int column doesn't accept null
into new_table 
from main_table;

drop table main_table;
rename table new_table TO main_table;