Oracle queries the information of database and table columns

-- View all tables of the current user in the Oracle database
Select table_name from user_tables;

-- View All tables under all users in the Oracle database
Select User, table_name from all_tables;

-- View all user columns in the Oracle database
Select table_name, column_name from user_tab_columns;

-- View all user columns in the Oracle database
Select User, table_name, column_name from all_tab_columns;
Displays all user columns in the database. The query results include the description, column name, type, and comments.
Select a. table_name, A. column_name, A. Comments from user_col_comments A, user_col_comments B where a. table_name = B. table_name and A. column_name = B. column_name;