Обсуждение: Dynamic SQL - transition from ms to pg

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Dynamic SQL - transition from ms to pg

От
Erik Darling
Дата:

Hi,

I've been developing for MS SQL around four years. I'm starting out with some work in Postgresql next week, and I'd like to know if there's any equivalent way to do something like this (from my word press)

http://sqldriver.wordpress.com/2013/12/09/generating-inserts-dynamically/

My question is mainly about creating comma delimited column names as variables and executing dynamic SQL with them. I've spent some time trying to find an answer and I seem to keep running into the same few stack questions.

Any advice is appreciated. I think I'm going to end up needing dynamic queries like what I've written for similar tasks moving data from files to staging tables and then to a larger set of data warehouse tables and setting up either views (perhaps materialized?) or more tables for reporting.

Thanks,
Erik

Re: Dynamic SQL - transition from ms to pg

От
Michael Paquier
Дата:



On Mon, Jan 6, 2014 at 2:13 PM, Erik Darling <edarling80@gmail.com> wrote:

Hi,

I've been developing for MS SQL around four years. I'm starting out with some work in Postgresql next week, and I'd like to know if there's any equivalent way to do something like this (from my word press)

http://sqldriver.wordpress.com/2013/12/09/generating-inserts-dynamically/

My question is mainly about creating comma delimited column names as variables and executing dynamic SQL with them. I've spent some time trying to find an answer and I seem to keep running into the same few stack questions.

Any advice is appreciated. I think I'm going to end up needing dynamic queries like what I've written for similar tasks moving data from files to staging tables and then to a larger set of data warehouse tables and setting up either views (perhaps materialized?) or more tables for reporting.

As far as I can understand from your script, you are use 2 parameters: an origin table and a target table. You could easily achieve that with a grammar similar to the script you are referring to using some pl/pgsql function, language which is pretty handy when generating queries on-the-fly in a procedure like what you are looking for:
http://www.postgresql.org/docs/devel/static/plpgsql.html
Regards,
--
Michael

Re: Dynamic SQL - transition from ms to pg

От
Pavel Stehule
Дата:
Hello



2014/1/6 Erik Darling <edarling80@gmail.com>

Hi,

I've been developing for MS SQL around four years. I'm starting out with some work in Postgresql next week, and I'd like to know if there's any equivalent way to do something like this (from my word press)

http://sqldriver.wordpress.com/2013/12/09/generating-inserts-dynamically/

My question is mainly about creating comma delimited column names as variables and executing dynamic SQL with them. I've spent some time trying to find an answer and I seem to keep running into the same few stack questions.

Any advice is appreciated. I think I'm going to end up needing dynamic queries like what I've written for similar tasks moving data from files to staging tables and then to a larger set of data warehouse tables and setting up either views (perhaps materialized?) or more tables for reporting.


It can look some like

CREATE OR REPLACE FUNCTION sample_insert_noflag(table_from text, table_to text, query_filter text)
RETURNS void AS $$
DECLARE
  sql text;
  column_names text;
BEGIN
  column_names = (SELECT string_agg(quote_ident(t.column_name), ',')
                    FROM information_schema.tables t
                   WHERE t.table_name = table_from
                     AND t.column_name <> 'STATUSFLAG');
  sql := format('INSERT INTO %I(%s) SELECT %s FROM %I %s',
             table_to, column_names, table_from, query_filter);
  RAISE NOTICE '%', sql;
  EXECUTE sql;
  RETURN;
END;
$$ LANGUAGE plpgsql STRICT;
 
Regards

Pavel Stehule

Thanks,
Erik


Re: Dynamic SQL - transition from ms to pg

От
Erik Darling
Дата:

Thank you Pavel. That's exactly what I needed to get started.

On Jan 6, 2014 3:25 AM, "Pavel Stehule" <pavel.stehule@gmail.com> wrote:
Hello



2014/1/6 Erik Darling <edarling80@gmail.com>

Hi,

I've been developing for MS SQL around four years. I'm starting out with some work in Postgresql next week, and I'd like to know if there's any equivalent way to do something like this (from my word press)

http://sqldriver.wordpress.com/2013/12/09/generating-inserts-dynamically/

My question is mainly about creating comma delimited column names as variables and executing dynamic SQL with them. I've spent some time trying to find an answer and I seem to keep running into the same few stack questions.

Any advice is appreciated. I think I'm going to end up needing dynamic queries like what I've written for similar tasks moving data from files to staging tables and then to a larger set of data warehouse tables and setting up either views (perhaps materialized?) or more tables for reporting.


It can look some like

CREATE OR REPLACE FUNCTION sample_insert_noflag(table_from text, table_to text, query_filter text)
RETURNS void AS $$
DECLARE
  sql text;
  column_names text;
BEGIN
  column_names = (SELECT string_agg(quote_ident(t.column_name), ',')
                    FROM information_schema.tables t
                   WHERE t.table_name = table_from
                     AND t.column_name <> 'STATUSFLAG');
  sql := format('INSERT INTO %I(%s) SELECT %s FROM %I %s',
             table_to, column_names, table_from, query_filter);
  RAISE NOTICE '%', sql;
  EXECUTE sql;
  RETURN;
END;
$$ LANGUAGE plpgsql STRICT;
 
Regards

Pavel Stehule

Thanks,
Erik