如果b条件不存在，则使用条件a进行Oracle SQL选择

Question

我被存在和不存在的关键字卡住。

我有一个表（Oracle门户表），其中有总结，以下结构：

ID LANGUAGE CAPTION 
1  NL   DUTCH CAPTION 
1  F   FRENCH CAPTION 
2  NL   DUTCH CAPTION 
3  F   FRENCH CAPTION 

我需要一个选择总是选择每个ID两行，即使A F行或NL行不存在。然后，该行应在列的语言不存在的语言，但与现有行的标题（用语言F）

进行选择，以便查询的输出应该是：

ID LANGUAGE CAPTION 
1  NL   DUTCH CAPTION 
1  F   FRENCH CAPTION 
2  NL   DUTCH CAPTION 
2  F   DUTCH CAPTION 
3  F   FRENCH CAPTION 
3  NL   FRENCH CAPTION 

这是可能？

非常好奇， ，已经是一个很大的感谢！

ps：我有这样的东西，但它完全不是我想要的。

SELECT id, language, display_name 
FROM portal.wwsbr_all_folders p 
WHERE caid = 55 
AND DISPLAY_IN_PARENT_FOLDER = 1 
AND ((upper(language) = 'NL' AND not exists (SELECT * FROM portal.wwsbr_all_folders p2 WHERE p.id = p2.id and language IN ('F'))) 
     OR 
     (upper(language) = 'F' AND not exists (SELECT * FROM portal.wwsbr_all_folders p2 WHERE p.id = p2.id and language IN ('NL'))) 
    ) 
AND parent_id = 4030963 
ORDER BY sub_folder_sequence 

编辑： 我得到正确的结果用下面的查询现在

(SELECT id, CASE language WHEN 'nl' THEN 'f' ELSE 'f' END lang, display_name 
FROM portal.wwsbr_all_folders p 
WHERE caid = 55 
AND DISPLAY_IN_PARENT_FOLDER = 1 
AND ((language = 'f' and exists(SELECT * FROM portal.wwsbr_all_folders p2 WHERE p2.id = p.id AND language = 'f')) 
    OR (language = 'nl' and not exists(SELECT * FROM portal.wwsbr_all_folders p2 WHERE p2.id = p.id AND language = 'f'))) 
AND parent_id = 4656102) 
UNION ALL 
(
SELECT id, CASE language WHEN 'f' THEN 'nl' ELSE 'nl' END lang, display_name 
FROM portal.wwsbr_all_folders p 
WHERE caid = 55 
AND DISPLAY_IN_PARENT_FOLDER = 1 
AND ((language = 'nl' and exists(SELECT * FROM portal.wwsbr_all_folders p2 WHERE p2.id = p.id AND language = 'nl')) 
    OR (language = 'f' and not exists(SELECT * FROM portal.wwsbr_all_folders p2 WHERE p2.id = p.id AND language = 'nl'))) 
AND parent_id = 4656102) 

Answer 1

您是否只有两种语言？如果是这样，你可以试试下面的解决方案：

WITH 
    my_data AS 
    (   SELECT 1 AS id, 'NL' AS language, 'DUTCH CAPTION' AS caption FROM dual 
     UNION ALL SELECT 1 AS id, 'F' AS language, 'FRENCH CAPTION' AS caption FROM dual 
     UNION ALL SELECT 2 AS id, 'NL' AS language, 'DUTCH CAPTION' AS caption FROM dual 
     UNION ALL SELECT 3 AS id, 'F' AS language, 'FRENCH CAPTION' AS caption FROM dual) 
SELECT 
     id, language, caption 
    FROM my_data md 
UNION ALL 
SELECT 
     id, DECODE(language, 'NL', 'F', 'NL'), caption 
    FROM my_data md 
WHERE NOT EXISTS (SELECT 1 
        FROM my_data 
        WHERE id = md.id 
        AND language != md.language) 
ORDER BY id, language; 

Answer 2

财产以后像下面这样。

如果你有一个额外的表，你可以使用它的ID是id_list而不是WITH部分。

WITH id_list AS 
(SELECT DISTINCT id FROM portal_table) 
SELECT * 
FROM 
(
    -- FRENCH 
    SELECT 
     i.id as id 
    , 'F' as language 
    , NVL(f.CAPTION, NL.CAPTION) AS CAPTION 
    FROM 
     id_list i 
     LEFT OUTER JOIN portal_table f ON (f.id = i.id AND f.language = 'F') 
     LEFT OUTER JOIN portal_table nl ON (nl.id = i.id AND nl.language = 'NL') 
    UNION 
     -- DUTCH 
    SELECT 
     i.id as id 
    , 'NL' as language 
    , NVL(NL.CAPTION, F.CAPTION) AS CAPTION 
    FROM 
     id_list i 
     LEFT OUTER JOIN portal_table f ON (f.id = i.id AND f.language = 'F') 
     LEFT OUTER JOIN portal_table nl ON (nl.id = i.id AND nl.language = 'NL') 
) 
order by id 
;