how to take backup of a child table with foreign key dependency in mysql using bash
Assuming MySQL 5.x

mysqldump has a --where option that can be used to limit/select rows to be backed up.

There isn't an option to join two tables using --where but you can identify which t_id values you want to backup and then run two mysqldumps as follows:

mysqldump -u... -p... --where="t_id in (10,100,200,300,.....)" database_name parent_table &gt; parent.sql

mysqldump -u... -p... --where="t_id in (10,100,200,300,.....)" database_name child_table &gt; child.sql

Once you have the parent.sql and child.sql dump files, load them into the target database and you should be good to go.

Also, note that I am assuming t_id column is indexed on both tables otherwise it may take a long time to dump the rows if the two tables have large number of rows.