从成员列表中排除用户列表（联合？）

Question

Your guidance is really appreciated on the following matter.

I am trying to display a list of users (to a user) by eliminating the users that already exist in other his/her lists.

For example, I want to display all my sites users to a user, minus his blocked list.

I believe I need to use the UNION operator, but have no previous experience in doing so.

would it be something like?

SELECT * FROM myMembers WHERE id='$id'
UNION
SELECT * FROM blocked WHERE id!='$id'
UNION
.
.
.

Just doesn't feel right... My database scheme is:

myMembers
-----------------------
id        username
-----------------------
1              x
2              y
3              z

Blocked
---------------------------------------------------------
id        mem1        mem2
---------------------------------------------------------
1              2              1
2              4              1

mem2 = the user doing the blocking.

Answer 1

SELECT * FROM myMembers WHERE id NOT IN (SELECT * FROM Blocked WHERE mem2!='$userid')

where userid is the id of the user to whom you are displaying the list