MySQL Dynamic Array Variable

#MySQL 5.7.12
#please drop objects you've created at the end of the script 
#or check for their existance before creating
#'\\' is a delimiter

#select version() as 'mysql version';
\\
set @ids := '3,1';
\\
select @ids;
\\
#create table samples (id int, name varchar(100));

desc samples;
\\
insert into samples values (1, 'a');
\\
insert into samples values (2, 'b');
\\
insert into samples values (3, 'c');
\\
#select * from samples;
\\
#select * from samples where id in (3,1);
\\

set @sql = concat("SELECT * FROM `samples` WHERE `samples`.Id in (" , @ids, ")");
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PREPARE stmt FROM @sql;
\\
EXECUTE stmt;