MySQL的@與@@區別

MySQL的@與@@區別

@x 是 用戶自定義的變量  (User variables are written as @var_name)

@@x 是 global或session變量  (@@global  @@session )

   

@@查看全局變量:

select   @@log_error;

 

 

@設置全局變量值:

mysql> SET @t1=0, @t2=0, @t3=0;

mysql> SELECT @t1:=(@t2:=1)+@t3:=4,@t1,@t2,@t3;