Determine if all IDs in the column of one data.frame are in a column of a data.frame in R

I have two data.frame tables in R. Both have IDs for users who took particular actions. The users in the second table should all have done the actions in the first table, but I want to confirm. What would be the best way to determine if all the IDs in table 2 are represented in table, and if not what IDs aren't?

Table A

**Unique ID**    **Count**
abc123           1
zyx456           15
888aaaa          4

Table B

**Unique ID**    **Count**
abc123           1
zyx456           1
zzzzz123         2

I'm trying to get a response that abc123 and zyx456 in Table B are in Table A and that zzzzz123 is not represented in Table A but is in B (which would be an error, since all B should be in A).