Re: COALESCE and GROUP BY and AGGREGATES

On Nov 13 10:49, Erik Jones wrote:
> Ok, here's a sample table for the question I have:
>
> CREATE TABLE sales_table (
> sale_type varchar default 'setup' not null,
> sale_amount numeric not null
> sale_date timestamp without timezone default now());
>
> So, let's say there are 3 different sale_types: 'setup', 'layaway',
> 'the_hookup' and I want to get totals for each type in a given month:
>
> SELECT sale_type, SUM(sale_amount)
> FROM sales_table
> WHERE sale_date LIKE '2006-11%'
> GROUP BY sale_type;
>
> If there hasn't been a sale of a given type in that month there won't be
> a row in the result set for that type. I want a row for each type with
> a default of 0 if there haven't been any sales for that type yet that
> month.

What about such a schema design:

CREATE TABLE sale_types (
id serial PRIMARY KEY,
name text NOT NULL DEFAULT 'setup'
);

CREATE UNIQUE INDEX sales_types_typ_idx ON sales_types (typ);

CREATE TABLE sales_table (
typ bigint REFERENCES sale_types (id),
amount numeric NOT NULL,
sdate timestamp without time zone DEFAULT CURRENT_TIMESTAMP
);

SELECT TYP.name, COALESCE(SUM(TBL.amount), 0)
FROM sale_types AS TYP
LEFT OUTER JOIN sales_table AS TBL ON (TYP.id = TBL.typ)
WHERE TBL.sale_date LIKE '2006-11%'
GROUP BY TYP.name;

I didn't try the above SQL queries, but I hope you understand what I
meant.

Regards.