Question

Please read both the SQL queries and tell me what they are saying/doing (step by step if you can)

a. Read the following, translate to "English and describe what question the auerv is SELECT Entertainers.EntstageName, FROMEntertainers INNER JOIN Engagements ON Entertainers.EntertainerlD Engagements.EntertainerlD b. Read the following, translate to "English and describe what question the query is answering. SELECT Musical Styles StylelD, Musical_Styles.StyleName, Customers.CustomerlD, Customers.CustFirstName, CustomersCust FROM Musical_Styles LEFT OUTER JOIN (Musical_Preferences INNER JOIN Customers ON Musical_Prefernces.CustomerID Customers Custome ON Musical_Styles.StylesID Musical Preferences.StylelD

Answer 1

a.
Here we have three SQL cluases which are select, from and where.

In the query we are selecting the attributes Entertainers.EntStageName, Engagements.StartDateEngagement.EndDate,
Engagements.ContractPrice from the a join but not a table.

This join is an INNER join of Engagements and Entertainers and for the condition to join them is
Engagements.EntertainerId=Entertainers.EntertainerId.

So the join will occur wherever the EntertainerId is same in both the tables Engagements and Entertainers.

From the result of the join operation we are selecting attributes.

b.

b.
Here also first we are selecting some attributs in the SELECT statement.

But in this case we have to joins.

If you observe there is a LEFT OUTER join and an INNER join.

First the join inside the brackets will happen, which is an INNER join.
Where we are joining Musical_Preferencesn table with Customers table on the condition that the CustomerId should
be equal in both the tables. So thi INNER join returns all the matched records from both the tables wherever CustomerId
is same. This result a joined data.

From the resulted data above we are joining with Musical_Styles, but this join is LEFT OUTER join on the condition that
StylesId from both the tables Musical_Preferencesn and Musical_Styles is same.
LEFT OUTER join returns all the records matched wherever StylesId is same and remaning records of the table that is placed
on the left side of the LEFT OUTER join statement with nulls for non-matching records.

From this resultant data we are retrieving some attributs.

Please comment if you need any help.