SQL & PL/SQL

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PL/SQL LOOPS

User_4G3I3Nov 1 2021

Lets I have two column data
Column one = ID say (101,102,103), Column two = payments say values ($20,$30$,$30 etc)
Each ID/Payment repeats multiple times, a good example is the installment payment of an item you are financing.
So a typical output will be
ID Payment
101 $20
101 $20
101 $20
102 $30
102 $30
103 $20
103 $30
etc
I have used a block of "explicit cursor" to fetch data using a loop. There is an "if statement" after DBMS_OUTPUT.PUT_LINE before "END LOOP"
the current "IF statement" I have goes like
IF cursor_name%rowcount = 1 then DBMS_OUTPUT...("First month payment"); end if; end loop;
Now, this method displays the if statement block only on the first row which is ID 101 payment $20.
What I want is to display the if statement message for every first occurrence of new ID, just the first payment. So how can I detect every new ID and display the message but only on the first row of the new ID?

Frank Kulash

Hi, User_4G3I3
Whenever you have a question, please post a little sample data (CREATE TABLE and INSERT statements for all tables involved, relevant columns only) so the people who want to help you can re-create the problem and test their ideas. For PL/SQL questions, include a complete working block that does the parts you already know how to do. Also post the exact results you want from that data, and explain why you want those results from that data. Always post your complete Oracle version (e.g. 18.4.0.0.0).
So how can I detect every new ID
Create a variable to hold the value of the previous id. Initialize it to something that can not be a value of id. Inside the beginning of the loop say

IF  id = prev_id THEN ...

At the end of the loop, say

prev_id := id;

Alternatively, you could add a column in the query that tells if a row is the first row for the id, using an analytic function such as LAG or ROW_NUMBER.

1 person found this helpful

Solomon Yakobson

First of all there is no row order in relational table. Order is provided vi ORDER [SIBLINGS] BY clause. So I will assume rows for same ID should be ordered by PAYMENT. Then there is no need to PL/SQL. All you need is:

SELECT  ID,
        MIN(PAYMENT)
  FROM  YOUR_TABLE
  GROUP BY ID
  ORDER BY ID
/

SY.

User_4G3I3

Sorry, I am new to this community and I will follow your guidelines next time :)
Here is the block of code. I am using the database from this textbook (Oracle 11g pl sql programming 2nd edition casteel)
SQL developer Version 21.2.1.204 Build 204.1703
Oracle Database 18c Enterprise Edition Release 18.0.0.0.0 - Production
example (1).JPG