SQL

oracle unique constraint

ALTER TABLE table_name ADD CONSTRAINT cst_name UNIQUE (col_name); 
ALTER TABLE table_name ADD CONSTRAINT cst_name UNIQUE (col1, col2); -- Multiple
ALTER TABLE table_name ADD col_name NUMBER UNIQUE;				  	-- New field

oracle sql unique

SELECT DISTINCT column_1
FROM table;
Code language: SQL (Structured Query Language) (sql)

oracle sql unique

SELECT
    DISTINCT product_id,
    quantity
FROM
    ORDER_ITEMS
ORDER BY
    product_id;
Code language: SQL (Structured Query Language) (sql)