SQLite conditional SELECT statement - multiple criteria but single statement - sql

Question

I have 2 tables, one is a list of customers, the other a list of historic and future delivery dates for these customers.
Convenience code to create example table:
CREATE TABLE Customers (
id INTEGER PRIMARY KEY AUTOINCREMENT,
name TEXT
);
INSERT INTO Customers (name) VALUES ('David');
INSERT INTO Customers (name) VALUES ('John');
INSERT INTO Customers (name) VALUES ('Anne');
CREATE TABLE Orders (
id INTEGER,
item TEXT,
delivery_date TEXT
);
INSERT INTO Orders VALUES ( 1, 'gopro' , '2016-04-05');
INSERT INTO Orders VALUES ( 1,'car', '2015-12-30');
INSERT INTO Orders VALUES ( 1,'watch', '2015-10-20');
INSERT INTO Orders VALUES ( 2, 'laptop', '2016-04-15');
INSERT INTO Orders VALUES ( 3, 'car', '2016-01-15');
INSERT INTO Orders VALUES ( 3,'cup', '2015-11-30');
I need to create a SQL statement that shows all customers and their most recent and next delivery date.
(Something like - SELECT * from Customers with recent and next item and date FROM Orders.)
Expected Result Table
Name, Most Recent Item, Recent Date, Next Item, Next Date
David, car, 2015-12-30, gopro, 2016-04-05
John, NULL, NULL, laptop, 2016-04-15
Anne, car, 2016-01-15, NULL, NULL
But the closest I can get with a single statement is:
SELECT
(SELECT o.item from Orders WHERE delivery_date < date('now') ORDER BY delivery_date DESC LIMIT 1) as Last_Item_Ordered,
(SELECT o.delivery_date from Orders WHERE delivery_date < date('now') ORDER BY delivery_date DESC LIMIT 1) as Last_Delivery_Date,
(SELECT o.item from Orders WHERE delivery_date >= date('now') ORDER BY delivery_date ASC LIMIT 1) as Next_Item_Ordered,
(SELECT o.delivery_date from Orders WHERE delivery_date >= date('now') ORDER BY delivery_date ASC LIMIT 1) as Next_Delivery_Date,
c.*
FROM (Orders o INNER JOIN Customers c ON c.id = o.id)
GROUP BY c.name
ORDER BY c.id;
and the Actual results are as this:
Last_Item_Ordered Last_Delivery_Date Next_Item_Ordered Next_Delivery_Date id name
watch 2015-10-20 watch 2015-10-20 1 David
laptop 2016-04-15 laptop 2016-04-15 2 John
cup 2015-11-30 cup 2015-11-30 3 Anne
Todays date is 21st February 2016, hence some values are expected to be NULL for the above customers future results.
If anyone can help, be greatly appreciated. thanks

Answer 1

You can use the following query:
SELECT (SELECT o.item
from Orders AS o
WHERE o.id = c.id AND delivery_date < date('now')
ORDER BY delivery_date DESC LIMIT 1) as Last_Item_Ordered,
(SELECT o.delivery_date
from Orders AS o
WHERE o.id = c.id AND delivery_date < date('now')
ORDER BY delivery_date DESC LIMIT 1) as Last_Delivery_Date,
(SELECT o.item
from Orders AS o
WHERE o.id = c.id AND delivery_date >= date('now')
ORDER BY delivery_date ASC LIMIT 1) as Next_Item_Ordered,
(SELECT o.delivery_date
from Orders AS o
WHERE o.id = c.id AND delivery_date >= date('now')
ORDER BY delivery_date ASC LIMIT 1) as Next_Delivery_Date,
c.*
FROM Customers c
ORDER BY c.id;
Demo here