check all columns in sql and get one code example

Example: sql all columns

-- MySQL
SELECT * 
FROM INFORMATION_SCHEMA.COLUMNS;

-- SQL Server (possible solution)
SELECT * 
FROM SYS.COLUMNS;

-- Oracle
SELECT * 
FROM ALL_TAB_COLS; -- (If you only want user-defined columns)
-- ALL_TAB_COLS : only user-defined columns
-- ALL_TAB_COLUMNS : both user-defined AND system columns