mysql：如何找不到记录时返回NULL结果？

Question

这里是MySQL的我做：

mysql> select "Le Café de la Mairie" as titre, "15 pl Mairie" as adresse1, id from ville where sound=soundex('FERTE SOUS JOUARRE') and cp='77260'; 
+-----------------------+--------------+-----+ 
| titre     | adresse1  | id | 
+-----------------------+--------------+-----+ 
| Le Café de la Mairie | 15 pl Mairie | 447 | 
+-----------------------+--------------+-----+ 
1 row in set (0.00 sec) 

mysql> select "Le Café de la Mairie" as titre, "15 pl Mairie" as adresse1, id from ville where sound=soundex('FERTE SOUS JOUARRE') and cp='77261'; 
Empty set (0.00 sec) 

mysql> 

这是我想要的东西：

mysql> select "Le Café de la Mairie" as titre, "15 pl Mairie" as adresse1, id from ville where sound=soundex('FERTE SOUS JOUARRE') and cp='77260'; 
+-----------------------+--------------+-----+ 
| titre     | adresse1  | id | 
+-----------------------+--------------+-----+ 
| Le Café de la Mairie | 15 pl Mairie | 447 | 
+-----------------------+--------------+-----+ 
1 row in set (0.00 sec) 

mysql> **(same query but dont find a record)**; 
+--------------+------------+------+ 
| titre  | adresse1 | id | 
+--------------+------------+------+ 
| NULL   | NULL  | NULL | 
+--------------+------------+------+ 

mysql> 

当然，我已经谷歌搜索&计算器。

Answer 1

SELECT 
    t.* 
FROM 
    (SELECT 1) AS dummy 
    LEFT JOIN 
    (SELECT ... your select here) AS t 
     ON TRUE ; 

所以，坚持使用问题：

SELECT 
    t.* 
FROM 
    (SELECT 1) AS dummy 
LEFT JOIN 
    (SELECT 
     "Le Café de la Mairie" as titre, 
     "15 pl Mairie" as adresse1, 
     id 
     FROM ville 
     WHERE sound=soundex('FERTE SOUS JOUARRE') 
     AND cp='77261') AS t 
ON TRUE;