：=运算符不使用mysql函数内的用户定义变量

对MySql服务器5.6.17执行以下行可以得到预期的结果：

SELECT @registered_countryCode := countrycode, @registered_gcmRegId := GCM_regid FROM slappdb.tb_register WHERE phonenumber = '123';

select @registered_countryCode, @registered_gcmRegId;

但是如果我在函数中包含这些行，我会在第一个：=运算符处得到一个语法错误：

DECLARE registered_countryCode SMALLINT;
DECLARE registered_gcmRegId VARCHAR(255);

SELECT registered_countryCode := countrycode, registered_gcmRegId := GCM_regid FROM slappdb.tb_register WHERE phonenumber = extracted_phoneNumber;

---

我做错了什么？在函数中使用带有：=运算符的用户定义变量似乎是个问题。

编辑1：

SELECT registered_countryCode := countrycode, 
       registered_gcmRegId := GCM_regid 
  FROM slappdb.tb_register 
 WHERE phonenumber = extracted_phoneNumber;

SELECT countrycode, GCM_regid 
  INTO registered_countryCode, registered_gcmRegId
  FROM slappdb.tb_register 
 WHERE phonenumber = extracted_phoneNumber;

drop function if exists today;

delimiter //

create function today() returns date
begin
  declare today date default null;

  select now() into @_now;

  select curdate() into today;

  return today;
end;
//

delimiter ;

select today();
+------------+
| today      |
+------------+
| 2014-05-19 |
+------------+
select @_now;
+---------------------+
| @_now               |
+---------------------+
| 2014-05-19 14:04:24 |
+---------------------+

对于在函数中使用本地变量或会话/用户变量没有这样的限制

使用

进入

将值复制到局部变量中

更改：

SELECT registered_countryCode := countrycode, 
       registered_gcmRegId := GCM_regid 
  FROM slappdb.tb_register 
 WHERE phonenumber = extracted_phoneNumber;

SELECT countrycode, GCM_regid 
  INTO registered_countryCode, registered_gcmRegId
  FROM slappdb.tb_register 
 WHERE phonenumber = extracted_phoneNumber;

drop function if exists today;

delimiter //

create function today() returns date
begin
  declare today date default null;

  select now() into @_now;

  select curdate() into today;

  return today;
end;
//

delimiter ;

select today();
+------------+
| today      |
+------------+
| 2014-05-19 |
+------------+
select @_now;
+---------------------+
| @_now               |
+---------------------+
| 2014-05-19 14:04:24 |
+---------------------+

至：

SELECT registered_countryCode := countrycode, 
       registered_gcmRegId := GCM_regid 
  FROM slappdb.tb_register 
 WHERE phonenumber = extracted_phoneNumber;

SELECT countrycode, GCM_regid 
  INTO registered_countryCode, registered_gcmRegId
  FROM slappdb.tb_register 
 WHERE phonenumber = extracted_phoneNumber;

drop function if exists today;

delimiter //

create function today() returns date
begin
  declare today date default null;

  select now() into @_now;

  select curdate() into today;

  return today;
end;
//

delimiter ;

select today();
+------------+
| today      |
+------------+
| 2014-05-19 |
+------------+
select @_now;
+---------------------+
| @_now               |
+---------------------+
| 2014-05-19 14:04:24 |
+---------------------+

示例：

SELECT registered_countryCode := countrycode, 
       registered_gcmRegId := GCM_regid 
  FROM slappdb.tb_register 
 WHERE phonenumber = extracted_phoneNumber;

SELECT countrycode, GCM_regid 
  INTO registered_countryCode, registered_gcmRegId
  FROM slappdb.tb_register 
 WHERE phonenumber = extracted_phoneNumber;

drop function if exists today;

delimiter //

create function today() returns date
begin
  declare today date default null;

  select now() into @_now;

  select curdate() into today;

  return today;
end;
//

delimiter ;

select today();
+------------+
| today      |
+------------+
| 2014-05-19 |
+------------+
select @_now;
+---------------------+
| @_now               |
+---------------------+
| 2014-05-19 14:04:24 |
+---------------------+

---

'='

和

'：='

用法之间存在差异

“=”

用于比较

“：=”

用于分配

更改您的查询，如下所示：

SELECT @registered_countryCode := countrycode, 
       @registered_gcmRegId    := GCM_regid 
FROM slappdb.tb_register 
WHERE phonenumber = '123';

select @registered_countryCode, @registered_gcmRegId;

---

你的答案是绝对正确的，经过一些实验后我意识到了这一点。不幸的是，就在你回答之前，我稍微改变了我的问题。很抱歉。知道我为什么不能在函数中使用：=吗？