PostgreSQL query I don't understand

Question

I'm sorry for my title, but it's totally right. I don't know PostgreSQL well, but I have to take over other person's application. I know SQL, so it's usually no problem to take over any application based on MSSQL, Oracle, MySQL, PostgreSQL, ... but here is some kind of PostgreSQL facet. Could anyone, please, explain this query to me?

select company_generate_course_template_fc
       ((select company_id from company order by 1 desc limit 1)::int)

score 2 · Accepted Answer · 2015-09-24 05:51:41Z

2

The query calls the function company_generate_course_template_fc() passing the result of the query: select company_id from company order by 1 desc limit 1 as an argument. The result is cast to an integer using ::int (see the manual for details)

Apart from the ::int part (and the different ways of limiting the result to a single row), this wouldn't be much different in other databases

The ANSI SQL equivalent of ::int would be cast(... as integer)

edited Sep 24, 2015 at 5:51

answered Sep 24, 2015 at 5:44

user330315

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1 Comment

Honza Over a year ago

I'm sorry, I think I was so stupid because of early morning :-[... When I've got another look at the query, I knew. Thank you again and I'm sorry for this question.

MichalD · Accepted Answer · 2015-09-24 05:44:00Z

0

If you are talking about ::int it's type casting from string (company_id) to integer value

answered Sep 24, 2015 at 5:44

MichalD

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