feat: add valid time exercises

sql/04-valid-time.answers.sql

@@ -0,0 +1,41 @@
+-- @conn xtdb
+
+-- 👇 Run this first
+-- @block
+INSERT INTO users (_id, address, phone_number, email) VALUES
+('John Doe',      '123 Evergreen Row', '555-1234', '[email protected]'),
+('Fiona Green',   '456 Maple Street',  '555-5678', '[email protected]'),
+('Alice Johnson', '789 Oak Avenue',    '555-8765', '[email protected]'),
+('Bob Brown',     '101 Pine Road',     '555-4321', '[email protected]'),
+('Evan Foster',   '202 Birch Lane',    '555-6789', '[email protected]'),
+('George Harris', '303 Cedar Drive',   '555-9876', '[email protected]');
+
+-- Q: Fiona has changed her phone number to '666-8683', update the table:
+-- @block
+UPDATE users
+SET phone_number = '666-8683'
+WHERE _id = 'Fiona Green';
+
+-- Q: Write a query to show how her phone number has changed over time and when in valid time
+-- @block
+SELECT phone_number, _valid_from
+FROM users FOR VALID_TIME all
+WHERE _id = 'Fiona Green';
+
+-- Q: A user joined us a year ago, insert them into the database from when they joined in valid time with the details:
+-- Name: 'Tony Felonius', email `[email protected]`, phone number `666-1111` and the address '404 Elm Street'
+-- @block
+INSERT users (_id, address, phone_number, email, _valid_from) VALUES
+('Tony Felonius', '404 Elm Street', '666-1111', '[email protected]', TIMESTAMP '2023-09-29T00:00:00Z');
+
+-- Q: Later they tell us that they were actually lived at the address '1234 Maple Lane' since 3 months ago, update the database
+-- @block
+UPDATE users FOR VALID_TIME FROM TIMESTAMP '2024-03-29T00:00:00Z'
+SET address = '1234 Maple Lane'
+WHERE _id = 'Tony Felonius';
+
+-- Q: 'Alice Johnson' has told us that her address is going to change in 3 months to '5678 Oakwood Avenue', update the database in the future
+-- @block
+UPDATE users FOR VALID_TIME FROM TIMESTAMP '2024-12-29T00:00:00Z'
+SET address = '5678 Oakwood Avenue'
+WHERE _id = 'Alice Johnson';

sql/04-valid-time.sql

@@ -0,0 +1,32 @@
+-- @conn xtdb
+
+-- 👇 Run this first
+-- @block
+INSERT INTO users (_id, address, phone_number, email) VALUES
+('John Doe',      '123 Evergreen Row', '555-1234', '[email protected]'),
+('Fiona Green',   '456 Maple Street',  '555-5678', '[email protected]'),
+('Alice Johnson', '789 Oak Avenue',    '555-8765', '[email protected]'),
+('Bob Brown',     '101 Pine Road',     '555-4321', '[email protected]'),
+('Evan Foster',   '202 Birch Lane',    '555-6789', '[email protected]'),
+('George Harris', '303 Cedar Drive',   '555-9876', '[email protected]');
+
+-- Q: Fiona has changed her phone number to '666-8683', update the table:
+-- @block
+UPDATE ...;
+
+-- Q: Write a query to show how her phone number has changed over time and when in valid time
+-- @block
+SELECT ...;
+
+-- Q: A user joined us a year ago, insert them into the database from when they joined in valid time with the details:
+-- Name: 'Tony Felonius', email `[email protected]`, phone number `666-1111` and the address '404 Elm Street'
+-- @block
+INSERT ...;
+
+-- Q: Later they tell us that they were actually lived at the address '1234 Maple Lane' since 3 months ago, update the database
+-- @block
+UPDATE ...;
+
+-- Q: 'Alice Johnson' has told us that her address is going to change in 3 months to '5678 Oakwood Avenue', update the database in the future
+-- @block
+UPDATE ...;