Askergaliyev 3 task. (#129)

* Task 1 Askergaliyev

* Fixed typo in Askergaliyev_1_1.sql

* Askergaliyev, task2 is solved.

* Askergaliyev 3 task.

task3/Askergaliyev_3_1.sql

@@ -0,0 +1,25 @@
+SELECT
+    customers.customer_rk,
+    customers.full_name,
+    full_name_popularity.popularity
+FROM (
+    SELECT 
+        customer_rk,
+        CONCAT(last_nm, ':', first_nm, ':', middle_nm) AS full_name
+    FROM
+        cd_customers
+    WHERE
+        valid_to_dttm = '5999-01-01 00:00:00'
+    ) AS customers
+LEFT JOIN (
+    SELECT
+        CONCAT(last_nm, ':', first_nm, ':', middle_nm) AS full_name,
+        COUNT(*) AS popularity
+    FROM
+        cd_customers
+    WHERE
+        valid_to_dttm = '5999-01-01 00:00:00'
+    GROUP BY
+        full_name
+    ) AS full_name_popularity
+ON customers.full_name = full_name_popularity.full_name

task3/Askergaliyev_3_2.sql

@@ -0,0 +1,25 @@
+SELECT
+    calendar_dt,
+    IFNULL(SUM(open_accounts), 0) AS num_open_accounts
+FROM
+    calendar
+LEFT JOIN (
+    SELECT
+        renewed_dt,
+        expiration_dt,
+        COUNT(*) AS open_accounts
+    FROM
+        account_periods
+    GROUP BY
+        renewed_dt, expiration_dt
+    ) AS open_close_dts
+ON renewed_dt <= calendar_dt AND calendar_dt < expiration_dt
+WHERE
+    calendar_dt BETWEEN (
+        SELECT 
+            MIN(renewed_dt)
+        FROM
+            account_periods
+    ) AND CURDATE()
+GROUP BY
+    calendar_dt

task3/Askergaliyev_3_3.sql

@@ -0,0 +1,38 @@
+SELECT
+    years.year_no,
+    IFNULL(left_table.n_opens, 0) AS n_opens,
+    IFNULL(left_table.n_prolongations, 0) AS n_prolongations,
+    IFNULL(right_table.n_increased_deposits, 0) AS n_increased_deposits
+FROM (
+    SELECT DISTINCT
+        year_no
+    FROM
+        calendar
+    ) AS years
+LEFT JOIN (
+    SELECT
+        YEAR(renewed_dt) AS action_year,
+        SUM(account_renewal_cnt = 1) AS n_opens,
+        SUM(account_renewal_cnt > 1) AS n_prolongations
+    FROM
+        account_periods
+	GROUP BY
+        action_year
+    ) AS left_table
+ON years.year_no = left_table.action_year
+LEFT JOIN (
+    SELECT
+        YEAR(former_table.renewed_dt) AS action_year,
+        COUNT(*) AS n_increased_deposits
+    FROM
+		account_periods AS former_table
+    INNER JOIN
+		account_periods AS latter_table
+	ON
+		former_table.account_rk = latter_table.account_rk
+		AND 2 * former_table.opening_amt > 3 * latter_table.opening_amt
+		AND former_table.account_renewal_cnt = latter_table.account_renewal_cnt + 1
+	GROUP BY
+		action_year
+    ) AS right_table
+ON years.year_no = right_table.action_year