DB-Nerdery-Challenges - Luis Moroco

.gitignore

@@ -1,3 +1,6 @@
 solutions.sql
 data.sql
-schema.sql
+schema.sql
+
+## Config
+*.yml

src/answers.sql

@@ -1,15 +1,137 @@
 -- Your answers here:
+
+----- UTIL FUNCTIONS
+CREATE OR REPLACE FUNCTION get_state_id_by_name(_state_name TEXT)
+    RETURNS INT
+    LANGUAGE plpgsql
+AS $$
+DECLARE
+    _state_id INT;
+BEGIN
+    SELECT
+        s.id
+    INTO _state_id
+    FROM states AS s
+    WHERE s.name = _state_name;
+
+    IF NOT FOUND THEN
+        RAISE EXCEPTION 'State not found [name=%]', _state_name;
+    END IF;
+
+    RETURN _state_id;
+END;
+$$;
+----- UTIL FUNCTIONS
+
 -- 1
+SELECT
+    c.name AS name,
+    COUNT(s.id) AS count
+FROM countries AS c
+    INNER JOIN states AS s
+        ON c.id = s.country_id
+GROUP BY c.id;
 
 -- 2
+SELECT COUNT(*)
+FROM employees AS e
+WHERE e.supervisor_id IS NULL;
 
 -- 3
+SELECT
+    c.name AS name,
+    o.address AS address,
+    COUNT(*) AS empleyees_count
+FROM employees AS e
+    INNER JOIN offices AS o
+        ON o.id = e.office_id
+    INNER JOIN countries AS c
+        ON c.id = o.country_id
+GROUP BY c.name, o.address
+ORDER BY empleyees_count DESC, c.name DESC
+LIMIT 5;
 
 -- 4
+SELECT
+    e.supervisor_id AS supervisor_id,
+    count(e.id) AS count
+FROM employees AS e
+WHERE e.supervisor_id IS NOT NULL
+GROUP BY e.supervisor_id
+ORDER BY count DESC
+LIMIT 3;
 
 -- 5
+CREATE OR REPLACE FUNCTION get_offices_count_by_state_name(_state_name TEXT)
+    RETURNS INT
+    LANGUAGE plpgsql
+AS $$
+DECLARE
+    _state_id INT;
+BEGIN
+    _state_id := get_state_id_by_name(_state_name);
+
+    RETURN (
+        SELECT COUNT(*)
+        FROM offices AS o
+        WHERE o.state_id = _state_id
+    );
+END;
+$$;
+
+SELECT get_offices_count_by_state_name('Colorado') AS list_of_office;
 
 -- 6
+SELECT
+    o.name AS name,
+    COUNT(e.id) AS employees_count
+FROM offices AS o
+    INNER JOIN employees AS e
+        ON o.id = e.office_id
+GROUP BY o.name
+ORDER BY employees_count DESC;
 
 -- 7
+WITH office_employee_count AS (
+    SELECT
+        o.address,
+        COUNT(e.id) AS employees_count
+    FROM offices AS o
+        INNER JOIN employees AS e
+            ON o.id = e.office_id
+    GROUP BY o.address
+)
+
+(
+    SELECT *
+    FROM office_employee_count
+    WHERE employees_count = (SELECT MAX(employees_count) FROM office_employee_count)
+    LIMIT 1
+)
+UNION
+(
+    SELECT *
+    FROM office_employee_count
+    WHERE employees_count = (SELECT MIN(employees_count) FROM office_employee_count)
+    LIMIT 1
+);
 
+-- 8
+SELECT
+    e.uuid as uuid,
+    CONCAT(e.first_name, ' ', e.last_name) AS full_name,
+    e.email AS email,
+    e.job_title AS job_title,
+    o.name AS company,
+    c.name AS country,
+    s.name AS state,
+    sup.first_name AS boss_name
+FROM employees AS e
+    INNER JOIN employees AS sup
+        ON e.supervisor_id = sup.id
+    INNER JOIN offices AS o
+        ON e.office_id = o.id
+    INNER JOIN states AS s
+        ON s.id = o.state_id
+    INNER JOIN countries AS c
+        ON c.id = o.country_id;

src/answers_2.sql

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+-- Challenge 2
+
+----- UTIL FUNCTIONS
+CREATE OR REPLACE FUNCTION get_account_by_id(_account_id UUID)
+    RETURNS RECORD
+    LANGUAGE plpgsql
+AS $$
+DECLARE
+    account RECORD;
+BEGIN
+    SELECT *
+    INTO account
+    FROM accounts AS a
+    WHERE a.id = _account_id;
+
+    IF NOT FOUND THEN
+        RAISE EXCEPTION 'Account not found [account_id=%]', _account_id;
+    END IF;
+
+    RETURN account;
+END;
+$$;
+
+CREATE OR REPLACE FUNCTION update_account(_account_id UUID, _mount DOUBLE PRECISION)
+    RETURNS VOID
+    LANGUAGE plpgsql
+AS $$
+BEGIN
+    UPDATE accounts
+    SET
+        mount = COALESCE(_mount, mount)
+    WHERE id = _account_id;
+END;
+$$;
+----- UTIL FUNCTIONS
+
+-- Exercise 1
+SELECT
+    a.type AS type,
+    SUM(a.mount) AS mount
+FROM accounts AS a
+GROUP BY a.type;
+
+-- Exercise 2
+WITH user_accounts_count AS (
+    SELECT
+        u.id AS id,
+        COUNT(*) AS accounts_count
+    FROM users AS u
+        LEFT JOIN accounts AS a
+            ON u.id = a.user_id
+    WHERE a.type = 'CURRENT_ACCOUNT'
+    GROUP BY u.id
+    HAVING COUNT(*) >= 2
+)
+
+SELECT COUNT(*)
+FROM user_accounts_count;
+
+-- Exercise 3
+SELECT
+    a.id AS id,
+    a.type AS type,
+    SUM(a.mount) as total_amount
+FROM accounts AS a
+GROUP BY a.id, a.type
+ORDER BY total_amount DESC
+LIMIT 5;
+
+-- Exercise 4
+WITH account_movements AS (
+    SELECT
+        m.account_from AS account,
+        m.type,
+        CASE
+            WHEN type = 'IN'
+                THEN m.mount
+            WHEN type IN ('OUT', 'TRANSFER', 'OTHER')
+                THEN -1 * m.mount
+            ELSE 0
+        END AS amount
+    FROM movements AS m
+    WHERE m.type IN ('IN', 'OUT', 'TRANSFER', 'OTHER')
+
+    UNION ALL
+
+    SELECT
+        m.account_to AS account,
+        m.type,
+        CASE
+            WHEN type = 'TRANSFER'
+                THEN m.mount
+            ELSE 0
+        END AS amount
+    FROM movements AS m
+    WHERE m.type = 'TRANSFER'
+),
+account_aggregated AS (
+    SELECT
+        am.account AS account_id,
+        SUM(am.amount) AS total_movements
+    FROM account_movements AS am
+    GROUP BY am.account
+)
+
+UPDATE accounts AS a
+SET
+    mount = a.mount + aa.total_movements
+FROM account_aggregated AS aa
+WHERE a.id = aa.account_id;
+
+SELECT
+    u.id,
+    u.name,
+    SUM(a.mount) AS amount
+FROM users AS u
+    INNER JOIN accounts AS a
+        ON u.id = a.user_id
+GROUP BY u.id, u.name
+ORDER BY amount DESC
+LIMIT 3;
+
+-- Exercise 5
+CREATE OR REPLACE FUNCTION handle_new_movement()
+    RETURNS TRIGGER
+    LANGUAGE plpgsql
+AS $$
+DECLARE
+    origin_account RECORD;
+    target_account RECORD;
+    amount DOUBLE PRECISION;
+BEGIN
+    amount := NEW.mount;
+    origin_account := get_account_by_id(NEW.account_from);
+
+    IF NEW.type IN ('TRANSFER') THEN
+        IF NEW.account_to IS NULL THEN
+            RAISE EXCEPTION 'A target account is required [type_movement=%]', NEW.type;
+        END IF;
+
+        target_account := get_account_by_id(NEW.account_to);
+    END IF;
+
+    IF NEW.type IN ('OUT', 'TRANSFER', 'OTHER') THEN
+        IF origin_account.mount < NEW.mount THEN
+            RAISE EXCEPTION 'Insufficient funds [origin_account_founds=%][required_amount=%]', origin_account.mount, amount;
+        END IF;
+
+        amount := -1 * amount;
+    END IF;
+
+    PERFORM update_account(NEW.account_from,  origin_account.mount + amount);
+    IF NEW.account_to IS NOT NULL THEN
+        PERFORM update_account(NEW.account_to,  target_account.mount + ABS(amount));
+    END IF;
+
+    RETURN NEW;
+END;
+$$;
+
+CREATE TRIGGER after_insert_movement
+AFTER INSERT ON movements
+FOR EACH ROW
+EXECUTE FUNCTION handle_new_movement();
+
+-- Exercise 6
+SELECT
+    u.*,
+    json_agg(mv) AS movements
+FROM users AS u
+    INNER JOIN accounts AS ac
+        ON ac.user_id = u.id
+    LEFT JOIN movements AS mv
+        ON mv.account_from = ac.id
+WHERE ac.id = '3b79e403-c788-495a-a8ca-86ad7643afaf'
+GROUP BY u.id;
+
+-- Exercise 7
+SELECT
+    u.name,
+    u.email
+FROM users AS u
+    JOIN accounts AS a
+        ON u.id = a.user_id
+WHERE a.mount = (
+    SELECT MAX(max_mount)
+    FROM (
+        SELECT MAX(a.mount) AS max_mount
+        FROM accounts AS a
+        GROUP BY a.user_id
+    ) AS subquery
+);
+
+-- Exercise 8
+SELECT
+    mv.*
+FROM users AS u
+    INNER JOIN accounts AS a
+        ON u.id = a.user_id
+    INNER JOIN movements AS mv
+        ON mv.account_from = a.id
+WHERE u.email = 'Kaden.Gusikowski@gmail.com'
+ORDER BY mv.type, mv.created_at;