Contact table for customers and employees
with this structure you can find every employye that a customer has, only by querying the Customercontacts table, and only if you need more details from the other tables you join them.
edit.
with this revision  Iadded a date so that you can search for a tine frame where the customer has contact with ione of the empoyees


CREATE TABLE customer (cid BIGINT PRIMARY KEY)




CREATE TABLE customerDeatails (
cdid BIGINT PRIMARY KEY
, cid BIGINT
, Details TEXT
,  FOREIGN KEY (cid) REFERENCES customer(cid) )




CREATE TABLE employee (eid BIGINT PRIMARY KEY)




CREATE TABLE CustomerContactss(
cid BIGINT
, eid BIGINT
,contactdate Datetime
, Details TEXT
, PRIMARY KEY (cid,eid,contactdate)
,  FOREIGN KEY (cid) REFERENCES customer(cid)
,FOREIGN KEY (eid) REFERENCES employee(eid))


db&lt;&gt;fiddle here