#用户变量
set @t = now();
SELECT DATE_FORMAT(NOW(),'%b %d %Y %h:%i %p')

#使用SET初始化用户变量
SET @ab = 'abcee';
SELECT @ab := 'fghi';
SELECT @ab;

#使用SELECT初始化用户变量并赋值
SELECT @var1 := '123456789';
SELECT @var1;

#判断存储过程是否存在并删除;
DROP PROCEDURE IF EXISTS MYpROC;

CREATE PROCEDURE MyProc
(
IN dMonth INT,            #会话变量
IN dDay INT,                #会话变量
OUT dTotalCount INT    #会话变量
)
begin
    #声明会话变量
    DECLARE MyVar int;
    
    SELECT @var1 := '9999999';
    #条件查询
    SELECT * from dc_log WHERE MONTH(AddTime) = dMonth AND Day(AddTime) = dDay;
    
    #通过SELECT……INTO语句赋值
    SELECT COUNT(1) INTO dTotalCount from dc_log WHERE MONTH(AddTime) = dMonth AND Day(AddTime) = dDay;
    
    #通过SET语句赋值
    SET MyVar = dTotalCount;
    
    #输出会话变量
    SELECT MyVar;
end

#调用存储过程
CALL myproc(9,21,@total);

#输出参数
select @total;


SELECT * from dc_log;