How to create read-only user for oracle schema

User hrqa_ro will be globally read only user.

SQL> conn / as sysdba
SQL> create user hrqa_ro identified by hrqa_ro123;
User created.

SQL> grant create session,select any dictionary,select any table to hrqa_ro;
Grant succeeded.

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Question:  I need to create a read-only user within my schema.  
How can you grant read-only access for a single user without granting read to every table?

Answer:  You can make any user read-only with the grant select any table privilege:

SQL> connect scott/tiger

SQL>create user scott_read_only_user identified by readonly;

SQL>grant create session to scott_read_only_user;

SQL>grant select any table to scott_read_only_user;

This will only grant read-only to scott tables, you would need to connect to another schema owner
to grant them read-only access.  Optionally, you can add read-only dictionary acces:

SQL>grant select any dictionary to scott_read_only_user;

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[oracle@testsrv]$ sqlplus / as sysdba

SQL> create user juser_read_only identified by test;
SQL> grant create session to user_read_only;
SQL> grant select any table to user_read_only;

Once you have granted these privileges you can connect as the new user.

SQL> conn user_ready_only/test
SQL> select * from scott.emp;

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM
---------- ---------- --------- ---------- --------- ---------- ----------
    DEPTNO
----------
      7369 SMITH      CLERK           7902 17-DEC-80        800
        20

      7499 ALLEN      SALESMAN        7698 20-FEB-81       1600        300
        30

If you wish to grant select on dictionary views then:

SQL> conn / as sysdba
SQL> grant select any dictionary to user_read_only;
If you wish the read_only user could select ddl of any objects belongs to any schema then:

SQL> grant SELECT_CATALOG_ROLE to user_read_only;
SQL> conn user_read_only