adding sql prblems

Author: shreyashji

52.AK- Data Analyst Take Home Assignment by A Startup Spotify Case Study.sql

@@ -0,0 +1,81 @@
+#CREATE table activityy
+(
+user_id char(20),
+event_name char(20),
+event_date date,
+country char(20)
+);
+#delete from activityy;
+#insert into activityy values (1,'app-installed','2022-01-01','India')
+,(1,'app-purchase','2022-01-02','India')
+,(2,'app-installed','2022-01-01','USA')
+,(3,'app-installed','2022-01-01','USA')
+,(3,'app-purchase','2022-01-03','USA')
+,(4,'app-installed','2022-01-03','India')
+,(4,'app-purchase','2022-01-03','India')
+,(5,'app-installed','2022-01-03','SL')
+,(5,'app-purchase','2022-01-03','SL')
+,(6,'app-installed','2022-01-04','Pakistan')
+,(6,'app-purchase','2022-01-04','Pakistan');
+#THe activity table shows the app-installed and app purchase activities fro spotify app along with country details
+select * from activityy;
+#Q.1 find totoal active users each day (Daily active users)
+select event_date,count(distinct user_id) from activityy a 
+group by event_date;
+
+# Q.2 find total active users each week (Weekly active users)
+#ssms only
+select *,datepart(week,event_date) from activityy;
+
+# Q.3 datewise total number of users who made the purchase same day they insatlled the app  (same day install and purchase)
+select user_id,event_date,count(distinct event_name) as  no_of_events from activityy 
+group by user_id,event_date having (count(distinct event_name))=2;
+#or
+select event_date,count(user_id) as no_of_users from (
+select user_id,event_date,count(distinct event_name) as  no_of_events from activityy 
+group by user_id,event_date having (count(distinct event_name))=2 ) a
+group by event_date;
+# final answer
+select event_date,count(new_user) as no_of_users from (
+select user_id,event_date,case when (count(distinct event_name))=2 then user_id else null end as new_user from activityy 
+group by user_id,event_date  #having (count(distinct event_name))=2 ) a
+) a
+group by event_date;
+
+#Q4. percentage of paid users in INDIA,USA AND ANY OTHER country should be tagged as others (country wise paid users)
+select case when country in('India','USA') then country else 'Others' end as new_country,count(distinct user_id) from activityy
+ where event_name = "app-purchase"
+ group by case when country in('India','USA') then country else 'Others' end ;
+ #cte
+ with country_wise_users as (
+ select case when country in('India','USA') then country else 'Others' end as new_country,count(distinct user_id) as user_cnt from activityy
+ where event_name = "app-purchase"
+ group by case when country in('India','USA') then country else 'Others' end ),
+ total as (select sum(user_cnt) as total_users from country_wise_users )
+ select 
+ new_country,user_cnt*1.0/total_users*100 as percent_users
+ from country_wise_users,total;
+ 
+ #Q.5 among All the users who installed the apps on a given day,how many did in app purchased on the very  next day --day wise result
+select *
+,lag(event_name,1) over(partition by user_id order by event_date) as prev_event_name
+,lag(event_date,1) over(partition by user_id order by event_date) as prev_event_date
+from activityy;
+#only ssms
+with prev_data as (
+select *
+,lag(event_name,1) over(partition by user_id order by event_date) as prev_event_name
+,lag(event_date,1) over(partition by user_id order by event_date) as prev_event_date
+from activityy)
+select * from prev_data
+ where event_name= 'app-purchase' and prev_event_name='app-installed' and datedifff(day,prev_event_date,event_date)=1
+ 
+ #
+ with prev_data as (
+select *
+,lag(event_name,1) over(partition by user_id order by event_date) as prev_event_name
+,lag(event_date,1) over(partition by user_id order by event_date) as prev_event_date
+from activityy)
+select event_date,count(distinct user_id) as cnt_users from prev_data
+where event_name= 'app-purchase' and prev_event_name='app-installed' and datedifff(day,prev_event_date,event_date)=1
+group by event_date

53. AK- Advance SQL Queries Consecutive Empty Seats.sql

@@ -0,0 +1,34 @@
+#create table bms (seat_no int ,is_empty varchar(10));
+#insert into bms values(1,'N'),(2,'Y'),(3,'N'),(4,'Y'),(5,'Y',(6,'Y'),(7,'N'),(8,'Y'),(9,'Y'),(10,'Y'),(11,'Y'),(12,'N'),(13,'Y'),(14,'Y');
+#3 OR MORE Consecutive Empty Seats
+#METHOD 1 -  LEAD/LAG
+select * from (
+SELECT *
+,LAG(is_empty,1) over(order by seat_no) as prev_1
+,LAG(is_empty,2) over(order by seat_no) as prev_2
+,Lead(is_empty,1) over(order by seat_no) as next_1
+,Lead(is_empty,2) over(order by seat_no) as next_2
+FROM BMS) A
+where is_empty = 'Y' and prev_1 = 'Y' and prev_2 = 'Y'
+or (is_empty = 'Y' and prev_1 = 'Y' and next_1 = 'Y')
+or (is_empty = 'Y' and next_1 = 'Y' and next_2 = 'Y') ;
+
+#method-2 Advance Aggregation
+select * from (
+SELECT *
+,sum(case when is_empty='Y' then 1 else 0 end) over(order by seat_no rows between 2 preceding and current row) as prev_2
+,sum(case when is_empty='Y' then 1 else 0 end) over(order by seat_no rows between 1 preceding and 1 following) as prev_next_1
+,sum(case when is_empty='Y' then 1 else 0 end) over(order by seat_no rows between current row and 2 following) as next_2
+FROM BMS) a 
+where prev_2=3 or prev_next_1=3 or next_2=3;
+
+#Method 3: Using ROW_NUMBER
+with diff_num as (
+select *
+,row_number() over(order by seat_no) as rn
+,seat_no-row_number() over(order by seat_no) as diff
+ from bms where is_empty='Y'),
+ cnt as (
+ select diff, count(1) as c from diff_num 
+ group by diff having count(1)>=3)
+ select * from diff_num where diff in (select diff from cnt) ;

57.How to generate match schedule for list of countries Match one row with all other rows.sql

@@ -1,9 +1,10 @@
 #How to generate match schedule for list of countries | Match one row with all other rows
 #create table countries (
-countryname varchar(20)
-);
+#countryname varchar(20)
+#);
 #dont match o the same values
 #insert into countries values('NewZealand'); #,'Australia','England','NewZealand')
 select * from countries a 
 inner join Countries b
-on a.countryname<b.countryname #it will eliminate one of the duplicate alpbabeticall les than b.countryname
+on a.countryname<b.countryname #it will eliminate one of the duplicate alpbabeticall les than b.countryname
+

58.Replace multiple commas with a single comma.sql

@@ -0,0 +1,7 @@
+#declare @var char(50) = 'abc,,def,,,,,,,,ghi,jkl,,,,,mno';
+#above is for ssms
+
+SET @var = 'abc,,def,,,,,,,,ghi,jkl,,,,,mno';
+#select replace(@var,  ',' , '*,') ;#every comma with * comma
+#select replace(replace(@var,  ',' , '*,'), ',*','');
+select replace(replace(replace(@var,  ',' , '*,'), ',*',''), '*,', ',') as ans;