ERROR 1414 (42000): OUT or INOUT argument 1 for routine mytest.getTotalUser is not a variable or NEW pseudo-variable in BEFORE trigger

MySQL存储过程出现：

ERROR 1414 (42000):

OUT or INOUT argument 1 for routine mytest.getTotalUser is not a variable or NEW pseudo-variable in BEFORE trigger

CALL  fun(a);

CALL  fun(@a);

 

SELECT @a;//获取变量值