Error while creating table : Syntax error at or near "#" - postgresql

Question

I am trying to convert SQL Server stored function to PostgreSQL stored function I am getting one syntactical error at declare #table1 table
CREATE OR REPLACE FUNCTION ETL_GetBuildingDetailsByUserID ( p_nInstID numeric=0)
RETURNS Boolean
AS $$
declare #table1 table
(
nbuilding numeric(18, 0) NOT NULL,
sbuild_name varchar(50) NULL,
sclient_build_id varchar(50) NULL,
nbuilding_inst_id numeric(18, 0) NOT NULL,
ntemp_building_id numeric(18,0) NULL,
nno_of_floors numeric(18,0) NULL
)
declare v_strDeptIds text;
v_strSubDeptIds text;
BEGIN
v_strsql := 'SELECT building.*
FROM building
WHERE (building.nbuilding_inst_id = '|| cast(p_nInstID as varchar(1)) ||')
';
print v_strsql
v_strsql1 text;
v_strsql1 := v_strsql
Insert into #table1; execute sp_executesql; v_strsql1
select * from #table1;
Return true;
END;
$$ LANGUAGE plpgsql;
Error
ERROR: syntax error at or near "#"
LINE 4: declare #table1 table
Can any one please tell what I am doing wrong?

Answer 1

It seems your function actually returns the result of a SELECT query, not a boolean value, so returns boolean is wrong to begin with.
To return a result, you need to declare the function as returns table(). But as you seem to simply return rows from the building table you can define it as returns setof building.
Then remove the useless dynamic SQL which seems completely unnecessary.
In PL/pgSQL there are no table variables, and copying the result of a query into one before returning that result from that table seems to be an unnecessary step which only slows down things. In Postgres you simply return the result of the query, there is no need to store it locally.
Additionally: rather than casting a parameter to another type inside the function it's better to declare that parameter with the type you expect.
So the simplified version of that function in PostgreSQL would be:
CREATE OR REPLACE FUNCTION ETL_GetBuildingDetailsByUserID ( p_nInstID text)
RETURNS setof building
AS $$
select building.*
from building
WHERE building.nbuilding_inst_id = p_nInstID
$$ LANGUAGE sql;
You can use it like this:
select *
from ETL_GetBuildingDetailsByUserID ('42');
Unrelated, but: using numeric(18,0) for columns that store values without decimals is overkill. You should define those columns as bigint. Much faster and uses less space than numeric.