read table i_regis2 with key cid eq s_validate-cid error

hi everyone:

im new to abap development and i am currently in the process of validating the fields on one table comparing them to another table.

right now this is the loop im using but i keep geting the same error when i try to assiociate a key field.

loop at i_index into s_validate.

read table i_regist2 with key cid eq s_validate-cid <------ "eq s_validate-cid" is not expected (Error message)

transporting no fields.

if sy_subrc eq 0.

...

...

...

please clarify why this is happening and what is needed to correct this error.

thanks in advance 😊