Re: [GENERAL] SELECT statement with sub-queries

On 28.05.2017 20:19, ml@ft-c.de wrote:
> Hallo,
>
> SELECT *
> FROM products
> WHERE exists
>       (SELECT categories.cat FROM categories WHERE
>       categories.serial==products.category);
        categories.serial = products.category);  -- one equal sign

> or
> SELECT * FROM products
> WHERE category IN
>        (SELECT categories.cat FROM categories);
>
> On 28.05.2017 19:03, Michelle Konzack 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?
>>
>>
>>
>>
>>
>>
>>
>
>