generic sql question

My question is it possible to speed up a query doing preselects? What I'm working on could end up being a very large dataset. I hope to have 100-1000 queries per second (0r more?), and if very large tables are joined with very large tables, I imagine that the memory would be get very full, overfull?

So in the schema below the following queries, usrs own articles, articles are of article types, issues have dates and names, and issues_published has an issue id and sets of articles, and article can be in many issues.

So if I wanted to find articles of a certain article type within a certain date range for the article and had actually been published, I believe that this query could find it, joining three tables and then doing the qualifications for date and type: (assume values in {} are escaped and proper syntax)

-----------------------------------------------------------------
SELECT article_id
FROM issues_published, issues, articles

WHERE issues_published.article_id = articles.article_id
AND
issues_published.issue_id = issues.issue_id
AND
articles.article_type = {article_type_id desired}
AND
article.article_date < {highest date}
AND
issues.article_date > {lowest date};

But would the following reduce the size of the join in memory?

SELECT article_id
FROM (select *
from articles
where article_date < {highest date}
AND
article_date > {lowest date} ) as articles_in_range, issues, issues_published

WHERE issues_published.article_id = articles_in_range.article_id
AND
issues_published.issue_id = issues.issue_id
AND
articles_in_range.article_type = {article type desired}

-------------------------------------------------------------------------
CREATE TABLE usr (
usr_id SERIAL NOT NULL,
PRIMARY KEY (usr_id)
);

CREATE TABLE article_types (
ariticle_type_id SERIAL NOT NULL,
article_type VARCHAR(40) NOT NULL,
PRIMARY KEY (ariticle_type_id)
);

CREATE TABLE articles (
article_id SERIAL NOT NULL,
ariticle_type_id INT4 NOT NULL,
author INT4 NOT NULL,
body TEXT NOT NULL,
date_written DATE NOT NULL,
PRIMARY KEY (article_id, ariticle_type_id, author)
);

CREATE TABLE issues (
issue_id SERIAL NOT NULL,
issue_title VARCHAR(40) NOT NULL,
issue_date DATE NOT NULL,
PRIMARY KEY (issue_id)
);

CREATE TABLE issues_published (
issue_id INT4 NOT NULL,
article_id INT4 NOT NULL,
PRIMARY KEY (issue_id, author, ariticle_type_id, article_id)
);

/*==========================================================================*/
/* Foreign Keys */
/*==========================================================================*/

ALTER TABLE articles
ADD FOREIGN KEY (author) REFERENCES usr (usr_id);

ALTER TABLE articles
ADD FOREIGN KEY (ariticle_type_id) REFERENCES article_types (ariticle_type_id);

ALTER TABLE issue_articles
ADD FOREIGN KEY (issue_id) REFERENCES issues (issue_id);

ALTER TABLE issue_articles
ADD FOREIGN KEY (author,ariticle_type_id,article_id) REFERENCES articles (author, ariticle_type_id, article_id);