draft: add polcies-w-gaps exercises

sql/00-policies-w-gaps.sql

@@ -0,0 +1,95 @@
+-- @conn xtdb
+-- Given the following policies
+-- @block
+INSERT INTO InsurancePolicies (
+    _id,
+    PolicyHolderName,
+    PolicyType,
+    PolicyDetails,
+    _valid_from,
+    _valid_to,
+    PremiumAmount,
+    CoverageAmount
+) VALUES
+    ('POL123456', 'John Doe',      'Health', {dob: DATE '1980-01-01'}, DATE '2024-01-01', DATE '2025-01-01', 1200.50, 100000.00),
+    ('POL123457', 'Jane Smith',    'Auto',   {dob: DATE '1985-02-02'}, DATE '2024-02-01', DATE '2025-02-01', 900.75,  50000.00),
+    ('POL123458', 'Alice Johnson', 'Life',   {dob: DATE '1970-03-03'}, DATE '2024-03-01', DATE '2044-03-01', 1500.00, 200000.00),
+    ('POL123459', 'Bob Brown',     'Home',   {dob: DATE '1990-04-04'}, DATE '2024-04-01', DATE '2025-04-01', 800.00,  150000.00),
+    ('POL123460', 'Charlie Davis', 'Health', {dob: DATE '1982-05-05'}, DATE '2024-05-01', DATE '2025-05-01', 1100.25, 120000.00),
+    ('POL123461', 'Diana Evans',   'Auto',   {dob: DATE '1988-06-06'}, DATE '2024-06-01', DATE '2025-06-01', 950.50,  60000.00),
+    ('POL123462', 'Evan Foster',   'Life',   {dob: DATE '1975-07-07'}, DATE '2024-07-01', DATE '2044-07-01', 1600.75, 250000.00),
+    ('POL123463', 'Fiona Green',   'Home',   {dob: DATE '1992-08-08'}, DATE '2024-08-01', DATE '2025-08-01', 850.00,  175000.00),
+    ('POL123464', 'George Harris', 'Health', {dob: DATE '1978-09-09'}, DATE '2024-09-01', DATE '2025-09-01', 1150.00, 130000.00),
+    ('POL123465', 'Hannah Jones',   'Auto',  {dob: DATE '1983-10-10'}, DATE '2024-10-01', DATE '2025-10-01', 1000.00, 70000.00);
+
+-- Which policy has nearly expired? (next 6 months say)
+-- @block
+SELECT _id, _valid_to
+FROM InsurancePolicies FOR VALID_TIME ALL
+WHERE _valid_to - INTERVAL 'P6M' < CURRENT_DATE;
+
+-- John Doe wants to buy insurance for 2025 now so that he doesn't have a period of no insurance
+-- How would you insert this new policy?
+-- @block
+INSERT INTO InsurancePolicies (
+    _id,
+    PolicyHolderName,
+    PolicyType,
+    PolicyDetails,
+    _valid_from,
+    _valid_to,
+    PremiumAmount,
+    CoverageAmount
+) VALUES
+    ('TODO');
+
+-- Answer:
+-- @block
+INSERT INTO InsurancePolicies (
+    _id,
+    PolicyHolderName,
+    PolicyType,
+    PolicyDetails,
+    _valid_from,
+    _valid_to,
+    PremiumAmount,
+    CoverageAmount
+) VALUES
+    ('POL123456', 'John Doe', 'Health', {dob: DATE '1980-01-01'}, DATE '2025-01-01', DATE '2026-01-01', 1200.50, 100000.00);
+
+-- Some others decide to buy policies also:
+-- @block
+INSERT INTO InsurancePolicies (
+    _id,
+    PolicyHolderName,
+    PolicyType,
+    PolicyDetails,
+    _valid_from,
+    _valid_to,
+    PremiumAmount,
+    CoverageAmount
+) VALUES
+    ('POL123457', 'Jane Smith',    'Auto',   {dob: DATE '1985-02-02'}, DATE '2025-03-01', DATE '2026-02-01', 900.75,  50000.00),
+    ('POL123458', 'Alice Johnson', 'Life',   {dob: DATE '1970-03-03'}, DATE '2044-03-01', DATE '2084-03-01', 1500.00, 200000.00),
+    ('POL123459', 'Bob Brown',     'Home',   {dob: DATE '1990-04-04'}, DATE '2025-04-02', DATE '2026-04-01', 800.00,  150000.00),
+    ('POL123460', 'Charlie Davis', 'Health', {dob: DATE '1982-05-05'}, DATE '2025-05-01', DATE '2027-04-01', 1100.25, 120000.00);
+
+-- Write a query to list policies that have been renewed
+-- @block
+SELECT p.*
+FROM InsurancePolicies FOR VALID_TIME ALL AS p
+JOIN InsurancePolicies FOR VALID_TIME ALL AS p_before
+    ON p._id = p_before._id
+        AND p_before._valid_time PRECEDES p._valid_time
+ORDER BY p._id
+
+-- When have gaps in their policy, and low long?
+-- @block
+SELECT p._id, p._valid_from - p_before._valid_to
+FROM InsurancePolicies FOR VALID_TIME ALL AS p
+JOIN InsurancePolicies FOR VALID_TIME ALL AS p_before
+    ON p._id = p_before._id
+        AND p_before._valid_time PRECEDES p._valid_time
+        AND NOT p_before._valid_time IMMEDIATELY PRECEDES p._valid_time
+
+--