Re: [GENERAL] SELECT statement with sub-queries

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От Amitabh Kant
Тема Re: [GENERAL] SELECT statement with sub-queries
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Msg-id CAPTAQBLC-imP1PixS0UNAwoOqErzT-svPOcwxHNLE2FnR88M0w@mail.gmail.com
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Ответ на [GENERAL] SELECT statement with sub-queries  (Michelle Konzack <linux4michelle@gmail.com>)
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On Sun, May 28, 2017 at 10:33 PM, Michelle Konzack <linux4michelle@gmail.com> wrote:
Hello *,

I try to get columns from my database with a singel SELECT, but I stuck.

I have 3 tables like:


1)  categories (serial,cat)

2)  manufacturers (serial,m_name)

3)  products (serial,category,manufacturer,p_name)


where the "category" and "manufacturer"
are numerical IDs from the two tables above.

So I like to replace the numerical IDs with the appropriated values,
mean

SELECT * FROM products WHERE category IN
    (SELECT categories.cat FROM categories WHERE
    categories.serial==products.category);

But I get:

ERROR:  operator does not exist: integer==integer
LINE1: ...gories.cat FROM categories WHERE  categories.serial==products.category);
                                                             ^
Hmm, "serial" is an "integer" and the "category" and "manufacturer" too.

So whats wrong with it?







--
Michelle Konzack        Miila ITSystems @ TDnet
GNU/Linux Developer     00372-54541400

Wouldn't a simple join like the one below suffice:

Select a.*,b.cat from products as a, categories as b where a.category=b.serial

or am I missing something?

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