Re: Comparing two tables of different database

2009/5/2 Isaac Dover <isaacdover(at)gmail(dot)com>

> i've not tried this in postgres, but using information_schema makes
> comparing structures of databases trivial. i've been using this query for a
> while with MSSQL. Maybe this helps to answer the question.
>
> - isaac
>
> select ST.Table_Name, ST.Column_Name, DV.Table_Name, DV.Column_Name, *
> from [database].information_schema.Columns ST
> full outer join [other database].information_schema.Columns DV
> on ST.Table_Name = DV.Table_name
> and ST.Column_Name = DV.Column_Name
> where ST.Column_Name is null or DV.Column_Name is NULL
>
>

Isaac, this query will return "ERROR: cross-database references are not
implemented".

Postgres does not support queries in databases other than current one. Even
a simple select * from otherdatabase.information_schema.columns will not
work and throw the same error.

However this can be done with dblink function like:

select ST.Table_Name, ST.Column_Name, DV.Table_Name, DV.Column_Name, *
from information_schema.Columns ST
full outer join dblink('dbname=otherdatabase','select Table_Name,
Column_Name from information_schema.Columns') DV(Table_Name text,
Column_Name text)
on ST.Table_Name = DV.Table_name
and ST.Column_Name = DV.Column_Name
where ST.Column_Name is null or DV.Column_Name is NULL

--
Lucas Brito