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Databases

sql query

Suppose there is a database with two tables namely Loans and Billpayment.

For the Loans table I have the following columns: loanId, clientId(primary key), DisbursementDate, applicationDate, approvalDate, loanNumber, loanAmount, interestRate

For the Billpayment table I have the following columns: billId(primary), customerId(foreign), billAmount, payment_status[success/fail] billDate

note: billdate in timestamp

bill is considered paid if payement status is 'success'

1 )How can I get the clients that had a bill payment in March 2018, 2) show the number of those clients that made at least one bill payment in the remaining months of 2018, 3) show whether or not the bill payment clients have a loan within 2018 or not

1 Answer

Brendan Whiting
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Brendan Whiting
Front End Web Development Techdegree Graduate 84,738 Points

You'll want to use a join. Something like this:

SELECT * FROM Loans 
    INNER JOIN Billpayment
    ON Loans. clientId = Billpayment.customerId
  /* some WHERE conditions... /*

You also may need to first create some subqueries or common table expressions to narrow down the results of one table before you join it. So you could have a subquery for "clients that had a bill payment in March 2018" and "clients that made at least one bill payment in the remaining months of 2018" and then join from that subquery.

thank you brendan ..but the approach i took is to create a temp table for customers that had a billpayement in march and futher more i used the IN clause to get the number of those clients that made at least one bill payment in the remaining months of 2018..but trying to show whether or not the bill payment clients have a loan within 2018 or not is where i keep getting stuck.. please can u kindly explain further with the approach u have taken

Brendan Whiting
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Brendan Whiting
Front End Web Development Techdegree Graduate 84,738 Points

Are you using a join anywhere?

It's hard for me to figure out the details without access to the data. The SQL Track here at Treehouse is very good. I also recommend this course on Codecademy: Analyzing Business Metrics.