Check out example codes for "sql all tables". It will help you in understanding the concepts better.

Code Example 1

-- Oracle
SELECT * 
FROM ALL_TABLES;

-- MySQL
SELECT * 
FROM INFORMATION_SCHEMA.TABLES;

Code Example 2

Showing all table: 
show tables;

Showing table data:
SELECT
* or column_names
FROM
table_name;

Code Example 3

SELECT TABLE_NAME
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_TYPE = 'BASE TABLE' AND TABLE_CATALOG=db_name() 
and TABLE_NAME like'%table_name%'--to check particular table

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