Sure, here are some SQL queries for all tables and fields in an Oracle database:

SQL

-- List all tables in the database.
SELECT table_name
FROM all_tables;

-- List all tables in the current user's schema.
SELECT table_name
FROM user_tables;

-- List all tables in the database, including the owner of the table.
SELECT table_name, owner
FROM all_tables;

-- List all tables in the database, including the owner of the table and the data type of each column.
SELECT table_name, owner, column_name, data_type
FROM all_tab_cols;

-- List all tables in the database, including the owner of the table, the data type of each column, and the default value for each column.
SELECT table_name, owner, column_name, data_type, default_value
FROM all_tab_cols;

To run these queries, you will need to connect to the Oracle database using a tool like SQLPlus. Once you are connected, you can run the query by typing it into the SQLPlus prompt.

For example, to run the first query above, you would type the following into the SQL*Plus prompt:

SQL

SELECT table_name
FROM all_tables;

This would return a list of all tables in the database.