How to store a set of values from another table in a field in MySQL -

How to store a set of values from another table in a field in MySQL -

i'm running on version of mysql not back upwards foreign key relationships.

suppose have 2 tables, 1 holds number of users while other 1 holds number of topics. want each of topics have field holds set of user id's participated in topic. read type set's documentation , says must values predefined values. how should go doing this?

you don't want field, inefficient way of storing such things. want new table.

in 3rd table (called, say, topicusers). have 2 fields: userid , topicid. can @ table , join info others needed.

this called normalisation

mysql set