insert .... on duplicate key...您可以使用语法来解决您的问题的唯一方法是 ifname并email制作一个复合键 - 我认为您最好使用 auto_increment 作为主键。
您可能需要在 PHP 中添加一些逻辑来首先进行检查，然后插入或更新 - 或编写一个函数来为您执行相同的测试 - 但两者都不是您可以触发的简单查询。
编辑：不确定这是否是您想要做的，但我认为满足您要求的最佳解决方案是在一对多关系中实际使用两个表。
Table-Users
id | email | name
create table users(
id int(10) not null auto_increment,
email varchar(100),
name varchar(100),
primary key(email, name)
);
Table-Ideas
id | userID | idea
create table users(
id int(10) not null auto_increment primary key,
userID int(10) not null,
idea text
);
使用桌子上的主键，您可以安全地执行操作，insert... duplicate...而不必担心覆盖人员。但是，第二个表将允许您将想法安全地存储给用户，并让您拥有每个用户的多个想法。由于关系users.id对ideas.userID您而言，即使他们的详细信息已更新，您也不会失去拥有它的人。
编辑：（又名，ZOMG facepalm）
$query="
update users
set name='".$userName."'
where
email='".$userEmail."'
and name is null";
编辑2：（又名，擦额头）
insert into users
select email, '".$namn."' from users where email='".$epost."'
on duplicate key
update name = values (name);
它在这里工作：
mysql> create table test1 (myName varchar(10) unique, myEmail varchar(10));
Query OK, 0 rows affected (0.02 sec)
mysql> insert into test1 values ('Tom','something');
Query OK, 1 row affected (0.01 sec)
mysql> insert into test1 values('Nick',null);
Query OK, 1 row affected (0.00 sec)
mysql> select * from test1;
+--------+-----------+
| myName | myEmail |
+--------+-----------+
| Tom | something |
| Nick | NULL |
+--------+-----------+
2 rows in set (0.00 sec)
mysql> insert into test1 select myName, myEmail from test1
where myName='Tom' on duplicate key update myEmail = values (myEmail);
Query OK, 0 rows affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> select * from test1;
+--------+-----------+
| myName | myEmail |
+--------+-----------+
| Tom | something |
| Nick | NULL |
+--------+-----------+
2 rows in set (0.00 sec)
mysql> insert into test1 select 'Tom', myEmail from test1
where myName='Tom' on duplicate key update myEmail = values (myEmail);
Query OK, 0 rows affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> select * from test1;
+--------+-----------+
| myName | myEmail |
+--------+-----------+
| Tom | something |
| Nick | NULL |
+--------+-----------+
2 rows in set (0.00 sec)
mysql> insert into test1 select myName, 'Something Else' from test1
where myName='Tom' on duplicate key update myEmail = values (myEmail);
Query OK, 2 rows affected, 1 warning (0.01 sec)
Records: 1 Duplicates: 1 Warnings: 1
mysql> select * from test1;
+--------+------------+
| myName | myEmail |
+--------+------------+
| Tom | Something |
| Nick | NULL |
+--------+------------+
2 rows in set (0.00 sec)
mysql> insert into test1 select myName, null from test1
where myName='Nick' on duplicate key update myEmail = values (myEmail);
Query OK, 0 rows affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> select * from test1;
+--------+------------+
| myName | myEmail |
+--------+------------+
| Tom | Something |
| Nick | NULL |
+--------+------------+
2 rows in set (0.00 sec)
mysql> insert into test1 select myName, 'yay' from test1
where myName='Nick' on duplicate key update myEmail = values (myEmail);
Query OK, 2 rows affected (0.01 sec)
Records: 1 Duplicates: 1 Warnings: 0
mysql> select * from test1;
+--------+------------+
| myName | myEmail |
+--------+------------+
| Tom | Something |
| Nick | yay |
+--------+------------+
2 rows in set (0.00 sec)
编辑3：试试这个$query
insert into table1 select coalesce(email,'".$epost."') as email, coalesce(name,'".$namn."') as name from table1
where email='".$epost."' on duplicate key update name = values (name);
