How to view users in oracle

How to view users in Oracle

Oracle is a very powerful database management system that is widely used in large enterprises. In Oracle, a common operation is to view users. However, for many beginners, this operation is not easy. In this article, we will introduce in detail how to view users in Oracle.

1. Use the system’s built-in command to view users

In Oracle, viewing the system’s built-in users is achieved by using SQL statements. First open the Oracle database, and then log in to the system administrator account:

SQL*Plus: Release 11.2.0.4.0 Production on Tue Oct 6 10:09:15 2019

Copyright (c) 1982, 2013, Oracle.  All rights reserved.

Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

Then, run the following SQL statement:

SQL> SELECT username FROM dba_users;

After executing the above statement, Oracle will list all the database entries currently in the database. User Info. These include session accounts, user accounts, Oracle system users, etc.

2. View the current session user

In Oracle, you can also know the name of the currently logged in user through the system variable $USER. This system variable is converted from the environment variable ORACLE_USER. The specific operation is as follows:

SQL> SET ECHO OFF
SQL> DEFINE USER = "& ORACLE_USER"
old   1: DEFINE USER = "&ORACLE_USER"
new   1: DEFINE USER = "scott"
SQL> SELECT '&USER' FROM dual;

The above statement will output the user name of the current session.

3. View all tables and columns

In addition to viewing user information, you can also view all tables and columns in Oracle. Execute the following statement to obtain a list of all current tables:

SQL> SELECT table_name FROM user_tables;

Execute the following statement to obtain a list of all current column information:

SQL> SELECT table_name, column_name FROM user_tab_columns;

The above statement will output the table names and sums of all current columns. Column name.

4. View user permissions

In addition to viewing user information and table columns, you can also view user permissions in Oracle. If you want to view the permission information of a specific user, you can run the following SQL statement:

SQL> SELECT privilege FROM dba_sys_privs WHERE grantee = 'username';

If you want to view the permissions of the user's current session, you can run the following SQL statement:

SQL> SELECT * FROM session_privs;

The above statement will be output Permission list information for the current session.

Summary

In this article, we discussed how to view users, session users, tables and columns, and user permissions in Oracle. These operations are a very important part of Oracle management. For beginners and novices, the content of this article should be very valuable. In practice, our continuous practice and mastery of these operations can not only help us better understand database management, but also greatly improve our work efficiency.

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