php從哪裏選擇多對偶

Question

我想插入一些數據到數據庫中。在插入過程中，我想首先做出一個判斷：如果title1不存在於table1和table2中，則插入。如何寫這個雙重句子？這是正確的嗎？或...謝謝。

mysql_query(" 
INSERT INTO table1 title 
SELECT '".$title."' 
FROM dual 
WHERE not exists (
    SELECT title 
    FROM table1 
    WHERE table1.title = '".$title."' 
) AND (
    SELECT title 
    FROM table2 
    WHERE table2.title = '".$title."' 
) "); 

Answer 1

首先，MySQL不使用dual表。只需直接選擇值。通常情況下，以插入一個表格，您只需要爲使用

INSERT INTO table1(title) SELECT 'something'; # or 
INSERT INTO table1(title) VALUES ('something'); 

但是，下面的使用由表（化名TT），以便能夠使用留在其加入到其它表。

mysql_query(" 
    INSERT INTO table1(title) 
    SELECT theTitle 
    FROM (SELECT '".$title."' theTitle) TT 
    LEFT JOIN table1 ON table1.title = TT.theTitle 
    LEFT JOIN table2 ON table2.title = TT.theTitle 
    WHERE table1.title is null and table2.title is null 
"); 

你也可以完成您的NOT EXISTS子句

mysql_query(" 
    INSERT INTO table1(title) 
    SELECT '".$title."' 
    WHERE NOT EXISTS (SELECT * FROM table1 WHERE title = '".$title."') 
     AND NOT EXISTS (SELECT * FROM table2 WHERE title = '".$title."') 
"); 

但我更喜歡前者，因爲這需要你使用$冠軍3次。

Answer 2

mysql_query("INSERT INTO table1 title 
       SELECT '".$title."' FROM dual 
       WHERE not exists (SELECT title FROM table1 WHERE table1.title = '".$title."') AND 
        not exists (SELECT title FROM table2 WHERE table2.title = '".$title."') "); 

失蹤查詢第二not exists。

Answer 3

聯盟任何人嗎？

mysql_query(" 
INSERT INTO table1 title 
SELECT '".addSlashes($title)."' 
FROM dual 
WHERE not exists (
    SELECT title 
    FROM table1 
    WHERE title = '".addSlashes($title)."' 
    UNION 
    SELECT title 
    FROM table2 
    WHERE title = '".addSlashes($title)."' 
) ");