Question

I have two table with this structure

categories
--------------------------------
id  | create
1   | 2012-12-01 12:00:00
2   | 2012-12-01 12:00:00

category_i18ns
--------------------------------
category_id     | lang  | title
1               | en    | home page
1               | de    | HomE PAGEa
1               | fa    | خانه
2               | en    | about

some categories have all languages data and some another havnt. for example category id 2 just have en translated title. i want to have a query that first check the current language for retrieve title and then if not exist then show another ones.

i have a query to get current category data with i18n data
in this current example de is default language. for category id 1 we have de title but for category 2 we dont. so i want english version as title of category

SELECT * FROM `mhf_swe_ndzhmju3_test`.`categories` AS `Category`
LEFT JOIN `mhf_swe_ndzhmju3_test`.`category_i18ns` AS `CategoryLocale` ON (
`CategoryLocale`.`category_id` = `Category`.`id`
AND `CategoryLocale`.`lang` = 'de')

desire out put for ‘de’ language

Category.id     CategoryLocale.title    CategoryLocale.lang
1               HomE PAGEa              de
2               about                   en

Answer 1

SELECT Category.id,
        COALESCE(a.lang, b.lang) lang,
        COALESCE(a.title, b.title) title
FROM   categories AS Category
      LEFT JOIN category_i18ns AS a
           ON a.category_id = Category.id AND a.lang = 'de'
      LEFT JOIN category_i18ns AS b
           ON b.category_id = Category.id AND b.lang = 'en'

• SQLFiddle Demo