adding sql problem from learn at knowstar

Author: shreyashji

36.17 How to identify Overlapping Date Ranges.sql

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+#https://www.youtube.com/watch?v=Ip6Ty2qmQXg&list=PL2-GO-f-XvjBl5fpzdfYaPW28PwsLzLc4&index=32
+#dont have data file 
+select emp.firstname,emp.lastname,emp.title,,emp.departmentname,emp.phone,emp.startdate,emp.enddate
+ from dbo.employee emp, dbo.employee emp1
+ where emp.firstname = emp1.firstname
+ and emp.lastname = emp1.lastname
+ and emp.startdate < emp1.startdate
+ and emp.enddate > emp1.startdate

36.18 Count the occurrence of a character in a string.sql

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+create table survey (
+surveyid int,
+response varchar(150)
+);
+#DROP TABLE survey;
+select * from survey;
+#insert into survey values (1,'ZZZZZXXXXCCCVVVBBNNMMLLKHJFGDFSDASASSAAQWEWERETRTYRYIYYIOIPUT');
+#insert into survey values (2,'QWPDHBCNFDHFFGALSDDCS');
+
+SELECT  surveyid,response,length(response) , replace(response,'Y',''), length(replace(response,'Y',''))
+ from survey;
+ 
+ 
+SELECT  surveyid,response,length(response) - length(replace(response,'Y','')) as stringoccured
+ from survey;

36.19 Find names that startend with More examples Like Pattern Matching.sql

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+select * from superstore_orders
+
+#start with A
+select Customer_Name from superstore_orders
+where Customer_Name like 'A%';
+#end with A
+select Customer_Name from superstore_orders
+where Customer_Name like '%A';
+
+#length with 3 char end last two char end with an,_specify single char
+select Customer_Name from superstore_orders
+where Customer_Name like '_an';
+
+#start with either a or c or d,SIGLE CHAR CONSTRAINT
+select Customer_Name from superstore_orders
+where Customer_Name like '[ACD]%';
+
+#start with RANGE
+select Product_Name from superstore_orders
+where Product_Name like '[A-P]%';
+#NOT BETWEEN A AND P
+select Product_Name from superstore_orders
+where Product_Name like '[^A-P]%';
+
+select ORDER_ID from superstore_orders;
+#3RD CHAR WOULD BE HIPHEN
+select ORDER_ID from
+ superstore_orders WHERE ORDER_ID LIKE '__-%';
+ 
+ #
+ SELECT PRODUCT_NAME from
+ superstore_orders
+ WHERE PRODUCT_NAME LIKE '%10[/]%'; 
+ 
+ 

36.20 How to find strings with lower case characters Case Insensitive Collate.sql

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+#How to find departments having only male / female employees
+# How to find strings with lower case characters | Case Insensitive | Collate
+
+select upper(FirstName) as uper_first,FirstName  from dbo.Emp 
+where upper(FirstName) COLLATE Latin1_Genral_CS_AS != FirstName;
+
+select SERVERPROPERTY('Collation')# CI MEANS CASE SENSITIVE

36.21 Difference between Countstar Count1 Countcolname.sql

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+#Difference between Count(*), Count(1), Count(colname) 
+#I have seen/heard select count(*) from tableA returns count of all rows in table regardless of whether a row has all null or some null values,
+#on the other hard select count(columnA) from tableA returns the number of records that do not have null in columnA. 
+#But what if we use a group by? I have seen no info on this. are they equivalent?
+select COUNT(*) from dbo.Emp;
+select COUNT(1) from dbo.Emp;
+#above both are same,in backend same execution plan is genrated for both
+
+#if null is there then it does not count,it will count not null values in that column
+select COUNT(lastname) from dbo.Emp; 

36.22 How to find Maximum of multiple columns.sql

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+#How to find Maximum of multiple columns 
+#ssmsonly
+select category,
+select max(saless)
+from (values([2015]),([2016]),([2017]),([2018]),([2019]),([2020]) as salestable(sales) ) as maxSales
+ from saless;
+ 
+ select * from (values (1), (2), (3), (4) ) as tbl(1);
+ 
+ #hardcoded values
+  select max(A) from (values (1), (2), (3), (4) ) as tbl(1);