Question

is it possible to create a MySQL Username that has permissions to only access data in a table with a certain value

e.g like the ‘root’ username a ‘user1’ which can access

ID    |   USER_ID    |  TEXT
======+==============+===============
1     |    1         | This is text a
2     |    1         | This is text b
3     |    2         | This is text c (hidden)
4     |    1         | This is text d

So that they would only be able to see ID 1,2 and 4 and the others would have no access, no results, or something like that?

Answer 1

You can do this by creating a view which excludes the records that MySQL user should not have access to:

/* Create a view that excludes records not belonging to USER_ID=1 */
CREATE VIEW restrict_vw AS (
  SELECT 
    ID,
    USER_ID,
    TEXT
  FROM tbl
  WHERE USER_ID = 1
);

/* Remove privileges from the underlying table */
REVOKE ALL ON dbname.tbl FROM user1@host;
/* And grant SELECT only on the view */
GRANT SELECT ON dbname.restrict_vw TO user1@host IDENTIFIED BY 'password';

The idea is to revoke all privileges from the database, which includes the underlying table, then grant SELECT privileges back to the view only. The privilege will not be transferred to the underlying table, and the user will therefore not have access to any records that are not exposed by the view.