How to store data from a SELECT statement and use that data to loop with an UPDATE statement - sql

Question

I am using PLSQL and I want to store the query results form SELECT statement in an array and then I want to loop using the elements from that array to UPDATE all the rows. The problem with the code below is that it returns a single-row. Sub-query returns more than one row because he is trying to set more than one variable in a row. Can you help me in this situation?
This is my code:
CREATE OR REPLACE PROCEDURE looping IS
BEGIN
FOR rec IN (SELECT IID FROM DATMCCN0)
LOOP
UPDATE DATMCCN0
SET E_NOME = (SELECT I_NOME FROM DAT_CCNCONFIG0 INNER JOIN DATMCCN0 ON DAT_CCNCONFIG0.I_NOME = DATMCCN0.CAPLIC where DATMCCN0.IID = rec.IID)
where IID = rec.IID;
END LOOP;
END;
EXECUTE looping;

Answer 1

You do not need a loop and can do it all in one MERGE statement (assuming your correlated query returns a single row for each IID):
CREATE OR REPLACE PROCEDURE looping
IS
BEGIN
MERGE INTO DATMCCN0 dst
USING (
SELECT b.IID,
I_NOME
FROM DAT_CCNCONFIG0 a
INNER JOIN DATMCCN0 b
ON a.I_NOME = b.CAPLIC
) src
ON ( src.IID = dst.IID)
WHEN MATCHED THEN
UPDATE SET E_NOME = src.I_NOME;
END;
If it does not then you will need to get only a single row, something like this:
CREATE OR REPLACE PROCEDURE looping
IS
BEGIN
MERGE INTO DATMCCN0 dst
USING (
SELECT b.IID,
MAX( I_NOME ) AS I_NOME
FROM DAT_CCNCONFIG0 a
INNER JOIN DATMCCN0 b
ON a.I_NOME = b.CAPLIC
GROUP BY b.IID
) src
ON ( src.IID = dst.IID)
WHEN MATCHED THEN
UPDATE SET E_NOME = src.I_NOME;
END;

Answer 2

One literal answer for your question "How to store data from a SELECT statement and use that data [to loop] with an UPDATE statement" would be a statement like this:
UPDATE
(SELECT src.E_NOME, dst.I_NOME
FROM DAT_CCNCONFIG0
JOIN DATMCCN0 src ON DAT_CCNCONFIG0.I_NOME = scr.CAPLIC
JOIN DATMCCN0 dst ON src.IID = dst.IID)
SET E_NOME = I_NOME;
However, it does not solve your problem that a single-row subquery returns more than one. Have a look at MT0's answer for that.