E-commerce Website SQL Analysis, PostgreSQL

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CREATE TABLE Ecommerce_customers
    ("customerid" int, "country" varchar(11))
;
    
INSERT INTO Ecommerce_customers
    ("customerid", "country")
VALUES
    (1, 'Germany'),
    (2, 'Mexico'),
    (3, 'Mexico'),
    (4, 'UK'),
    (5, 'Sweden'),
    (6, 'Germany'),
    (7, 'France'),
    (8, 'Spain'),
    (9, 'France'),
    (10, 'Canada'),
    (11, 'UK'),
    (12, 'Argentina'),
    (13, 'Mexico'),
    (14, 'Switzerland'),
    (15, 'Brazil'),
    (16, 'UK'),
    (17, 'Germany'),
    (18, 'France'),
    (19, 'UK'),
    (20, 'Austria')
;

CREATE TABLE Ecommerce_categories
    ("categoryid" int, "categoryname" varchar(14))
;
    
INSERT INTO Ecommerce_categories
    ("categoryid", "categoryname")
VALUES
    (1, 'Beverages'),
    (2, 'Condiments'),
    (3, 'Confections'),
    (4, 'Dairy Products'),
    (5, 'Grains/Cereals'),
    (6, 'Meat/Poultry'),
    (7, 'Produce'),
    (8, 'Seafood')
;

CREATE TABLE Ecommerce_employees
    ("employeeid" int, "birthdate" timestamp)
;
    
INSERT INTO Ecommerce_employees
    ("employeeid", "birthdate")
VALUES
    (1, '1968-12-08'),
    (2, '1952-02-19'),
    (3, '1963-08-30'),
    (4, '1958-09-19'),
    (5, '1955-03-04')
;

CREATE TABLE Ecommerce_orderdetails
    ("orderid" int, "productid" int, "quantity" int)
;
    
INSERT INTO Ecommerce_orderdetails
    ("orderid", "productid", "quantity")
VALUES
    (10248, 11, 12),
    (10248, 42, 10),
    (10248, 72, 5),
    (10249, 14, 9),
    (10249, 51, 40),
    (10250, 41, 10),
    (10250, 51, 35),
    (10250, 65, 15),
    (10251, 22, 6),
    (10251, 57, 15),
    (10251, 65, 20),
    (10252, 20, 40),
    (10252, 33, 25),
    (10252, 60, 40),
    (10253, 31, 20),
    (10253, 39, 42),
    (10253, 49, 40),
    (10254, 24, 15),
    (10254, 55, 21),
    (10254, 74, 21),
    (10255, 2, 20),
    (10255, 16, 35),
    (10255, 36, 25),
    (10255, 59, 30),
    (10256, 53, 15),
    (10256, 77, 12),
    (10257, 27, 25),
    (10257, 39, 6),
    (10257, 77, 15),
    (10258, 2, 50),
    (10258, 5, 65),
    (10258, 32, 6),
    (10259, 21, 10),
    (10259, 37, 1),
    (10260, 41, 16),
    (10260, 57, 50),
    (10260, 62, 15),
    (10260, 70, 21),
    (10261, 21, 20),
    (10261, 35, 20),
    (10262, 5, 12),
    (10262, 7, 15),
    (10262, 56, 2),
    (10263, 16, 60),
    (10263, 24, 28),
    (10263, 30, 60),
    (10263, 74, 36),
    (10264, 2, 35),
    (10264, 41, 25),
    (10265, 17, 30),
    (10265, 70, 20),
    (10266, 12, 12),
    (10267, 40, 50),
    (10267, 59, 70),
    (10267, 76, 15),
    (10268, 29, 10),
    (10268, 72, 4),
    (10269, 33, 60),
    (10269, 72, 20),
    (10270, 36, 30),
    (10270, 43, 25),
    (10271, 33, 24),
    (10272, 20, 6),
    (10272, 31, 40),
    (10272, 72, 24),
    (10273, 10, 24),
    (10273, 31, 15),
    (10273, 33, 20),
    (10273, 40, 60),
    (10273, 76, 33),
    (10274, 71, 20),
    (10274, 72, 7),
    (10275, 24, 12),
    (10275, 59, 6),
    (10276, 10, 15),
    (10276, 13, 10),
    (10277, 28, 20),
    (10277, 62, 12),
    (10278, 44, 16),
    (10278, 59, 15),
    (10278, 63, 8),
    (10278, 73, 25),
    (10279, 17, 15),
    (10280, 24, 12),
    (10280, 55, 20),
    (10280, 75, 30),
    (10281, 19, 1),
    (10281, 24, 6),
    (10281, 35, 4),
    (10282, 30, 6),
    (10282, 57, 2),
    (10283, 15, 20),
    (10283, 19, 18),
    (10283, 60, 35),
    (10283, 72, 3),
    (10284, 27, 15),
    (10284, 44, 21),
    (10284, 60, 20),
    (10284, 67, 5)
;

CREATE TABLE Ecommerce_orders
    ("orderid" int, "customerid" int)
;
    
INSERT INTO Ecommerce_orders
    ("orderid", "customerid")
VALUES
    (10248, 90),
    (10249, 81),
    (10250, 34),
    (10251, 84),
    (10252, 76),
    (10253, 34),
    (10254, 14),
    (10255, 68),
    (10256, 88),
    (10257, 35),
    (10258, 20),
    (10259, 13),
    (10260, 55),
    (10261, 61),
    (10262, 65),
    (10263, 20),
    (10264, 24),
    (10265, 7),
    (10266, 87)
;

CREATE TABLE Ecommerce_products
    ("productid" int, "categoryid" int, "price" int)
;
    
INSERT INTO Ecommerce_products
    ("productid", "categoryid", "price")
VALUES
    (1, 1, 18),
    (2, 1, 19),
    (3, 2, 10),
    (4, 2, 22),
    (5, 2, 21.35),
    (6, 2, 25),
    (7, 7, 30),
    (8, 2, 40),
    (9, 6, 97),
    (10, 8, 31),
    (11, 4, 21),
    (12, 4, 38),
    (13, 8, 6),
    (14, 7, 23.25),
    (15, 2, 15.5),
    (16, 3, 17.45),
    (17, 6, 39),
    (18, 8, 62.5),
    (19, 3, 9.2),
    (20, 3, 81),
    (21, 3, 10),
    (22, 5, 21),
    (23, 5, 9),
    (24, 1, 4.5),
    (25, 3, 14),
    (26, 3, 31.23),
    (27, 3, 43.9),
    (28, 7, 45.6),
    (29, 6, 123.79),
    (30, 8, 25.89),
    (31, 4, 12.5),
    (32, 4, 32),
    (33, 4, 2.5),
    (34, 1, 14),
    (35, 1, 18),
    (36, 8, 19),
    (37, 8, 26),
    (38, 1, 263.5),
    (39, 1, 18),
    (40, 8, 18.4),
    (41, 8, 9.65),
    (42, 5, 14),
    (43, 1, 46),
    (44, 2, 19.45),
    (45, 8, 9.5),
    (46, 8, 12),
    (47, 3, 9.5),
    (48, 3, 12.75),
    (49, 3, 20)
;

--select * from Ecommerce_customers limit 10;
--select * from Ecommerce_categories limit 10;
--select * from Ecommerce_employees limit 10;
--select * from Ecommerce_orderdetails limit 10;
--select * from Ecommerce_orders limit 10;
--select * from Ecommerce_products limit 10;

--#1 union & union all difference: duplicate values
select customerid
from Ecommerce_customers
union all
select customerid
from Ecommerce_orders


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