Oracle旧Lelft联接语法（+；）在联接条件中使用Like运算符

这在Oracle 8i上（请参见问题底部的注释）

我正在字符串上匹配关键字。如果一个特定字符串与多个关键字匹配，它将产生两行或多行。但我还想捕获结果中不匹配的字符串

考虑以下几点：

SELECT
    FREE_TEXT.*,
    KEYWORDS.KEYWORD    
FROM
    (
        (SELECT 1 AS ID, 'I like potatoes' AS TXT FROM DUAL) UNION
        (SELECT 2 AS ID, 'I like peppers' AS TXT FROM DUAL) UNION
        (SELECT 3 AS ID, 'I like potatoes, peppers' AS TXT FROM DUAL) UNION
        (SELECT 4 AS ID, 'I like onions' AS TXT FROM DUAL)
    ) FREE_TEXT,    
    (
        (SELECT 1 AS ID, 'potato' AS KEYWORD FROM DUAL) UNION
        (SELECT 2 AS ID, 'pepper' AS KEYWORD FROM DUAL) UNION
        (SELECT 3 AS ID, 'carrot' AS KEYWORD FROM DUAL)
    ) KEYWORDS  
WHERE
    FREE_TEXT.TXT LIKE ('%' || KEYWORDS.KEYWORD || '%') 
ORDER BY
    FREE_TEXT.ID

ID  TXT                         KEYWORD
1   I like potatoes             potato
2   I like peppers              pepper
3   I like potatoes, peppers    potato
3   I like potatoes, peppers    pepper

此代码产生以下结果：

SELECT
    FREE_TEXT.*,
    KEYWORDS.KEYWORD    
FROM
    (
        (SELECT 1 AS ID, 'I like potatoes' AS TXT FROM DUAL) UNION
        (SELECT 2 AS ID, 'I like peppers' AS TXT FROM DUAL) UNION
        (SELECT 3 AS ID, 'I like potatoes, peppers' AS TXT FROM DUAL) UNION
        (SELECT 4 AS ID, 'I like onions' AS TXT FROM DUAL)
    ) FREE_TEXT,    
    (
        (SELECT 1 AS ID, 'potato' AS KEYWORD FROM DUAL) UNION
        (SELECT 2 AS ID, 'pepper' AS KEYWORD FROM DUAL) UNION
        (SELECT 3 AS ID, 'carrot' AS KEYWORD FROM DUAL)
    ) KEYWORDS  
WHERE
    FREE_TEXT.TXT LIKE ('%' || KEYWORDS.KEYWORD || '%') 
ORDER BY
    FREE_TEXT.ID

ID  TXT                         KEYWORD
1   I like potatoes             potato
2   I like peppers              pepper
3   I like potatoes, peppers    potato
3   I like potatoes, peppers    pepper

我想做一个左连接，以便另外获得此行：

ID  TXT                         KEYWORD
4   I like onions               NULL

但是，以下语法使用旧的Oracle方法，即使用（+）进行左连接：

不工作并抛出

ORA-00933:SQL命令未正确结束

我使用的是Oracle8i，因此无法使用ANSI-92SQL连接语法

---

注意：我清楚地知道8i已经过时了，但我无法控制它。

外部联接运算符位于错误的位置；试一试

WHERE FREE_TEXT.TXT LIKE ('%' || KEYWORDS.KEYWORD (+) || '%') 

---

这管用！这种语法非常有意义，尽管起初出于某种原因我觉得它很奇怪。