I am trying to convert this if statement from SQL Server to Postgres:
IF COL_LENGTH('Flex','revision') IS NOT NULL and OBJECT_ID(N'df_revision', N'D') IS NULL
BEGIN
ALTER TABLE Flex ADD CONSTRAINT df_revision DEFAULT 0 FOR revision
END
The purpose of this query is to set the default on the revision column if the table has that column.
Postgres has default values for columns. Those aren't "constraints".
To change the default value of a column you use:
alter table flex alter column revision set default 0;
If for some strange reason you don't know if the column exists in the table, you can use a PL/pgSQL block:
do
$$
begin
if exists (select *
from information_schema.columns
where table_name = 'flex'
and column_name = 'df_revision')
then
alter table flex alter column revision set default 0;
end if;
end;
$$
;
