How to insert updated rows in a new table on DB2 - IBM - sql

Question

I need to create an update using sql dynamic and all the updated rows have to be sent in a log table.
In microsoft, i can use OUTPUT clause and it inserts the updated rows in a table, but how can i do this in db2, using sql dynamic?
I have the following tables:
AllCustomers - contains all customers from a db
Id
Name
1
John
2
Test
gdpr_id. - contains all customers which should be updated
Id
Name
1
John
gdpr_log - should contain the output of the update stmt
Id
Name
1
John
I found the below syntax , but it just displays the results.
SELECT fields FROM FINAL TABLE
(update table set field = 'value' where id ='xyz')
I tried to create another dynamic stmt as
INSERT INTO
SELECT fields FROM FINAL TABLE
(update table set field = 'value' where id ='xyz')
and the syntax is not recognized.
How can i replace it to insert all the updated values in a log table?
I have to use sql dynamic because the tables which need to be updated are stored in a metadata table and with a cursor, i create the update script for each line from the metadata table.
UPDATE:
Metadata table looks like this:
table
column
AllCustom
Name
AllCustom
Lastname
CREATE OR REPLACE PROCEDURE sp_test ()
DYNAMIC RESULT SETS 1
P1: BEGIN
--*****************VARIABLES *****************
DECLARE EOF INT DEFAULT 0;
declare v_table nvarchar(50);
declare v_column nvarchar(50);
declare v_rowid nvarchar(50);
declare v_stmt nvarchar(8000);
declare s1 statement;
--*****************UPDATE STEP *****************
-- Declare cursor
DECLARE cursor1 CURSOR WITH HOLD WITH RETURN FOR
SELECT table,column FROM metadata_tbl;
declare c1 cursor for s1;
DECLARE CONTINUE HANDLER FOR NOT FOUND
SET EOF = 1;
OPEN cursor1;
WHILE EOF = 0 DO
FETCH FROM cursor1 INTO v_table,v_column;
SET v_stmt = 'WITH A AS
(
SELECT name
FROM FINAL TABLE
(
UPDATE ' || v_table || ' set ' || v_column || ' = ''some name'' where id in (select ID from gdpr_id )
)
)
SELECT COUNT (1) as tst
FROM FINAL TABLE
(
INSERT INTO GDPR_LOG (table,name, LOGDATE)
SELECT ''' || v_table || ''', name, current_timestamp from A
) B';
PREPARE s1 FROM v_stmt ;
open c1 using v_table,v_column;
close c1;
END WHILE;
CLOSE cursor1;
END P1
Update step works fine, insert step duplicates the rows inserted.
What should I do to have the insert step ok?

Answer 1

You have to use SELECT as an outermost statement and keep inner SELECTs in distinct CTEs, if you have a number of them.
Try this:
WITH A AS
(
SELECT ID, NAME
FROM FINAL TABLE
(
UPDATE GDPR
SET NAME = 'Some name'
WHERE ID = 1
)
)
SELECT COUNT (1)
FROM FINAL TABLE
(
INSERT INTO GDPR_LOG (ID, NAME)
SELECT * FROM A
) B
Update:
Using dynamic SQL.
You must enclose the whole statement with some statement termination character (say, #) different from the default one (;) if you use some tool to run this compound statement and specify this statement terminator correctly there.
BEGIN
DECLARE C1 CURSOR FOR S1;
PREPARE S1 FROM
'
WITH A AS
(
SELECT ID, NAME
FROM FINAL TABLE
(
UPDATE GDPR
SET NAME = ?
WHERE ID = ?
)
)
SELECT COUNT (1)
FROM FINAL TABLE
(
INSERT INTO GDPR_LOG (ID, NAME)
SELECT * FROM A
) B
';
OPEN C1 USING 'Name', 1;
CLOSE C1;
END