How to generate SQL Code to update 9k rows with values for one column - sql

Question

I need to update one field for 9000 rows with random information on it.
Keep in mind that the table in question does not have Primary Key.
What's the best option to do it?
Thanks in advance.

Answer 1

Create table to hold 9000 random numbers for demonstration purposes:
CREATE TABLE brianl.random
(
VALUE NUMBER
, id INTEGER
);
Insert 9000 rows into the table
Since this is for demonstration purposes, I decided to use a PL/SQL loop as it is easy to understand even if you are not familiar with PL/SQL. I could just as easily used a Common Table Expression (CTE), but if you don't understand the PL/SQL, you won't understand the CTE
DECLARE
l_cnt INTEGER;
BEGIN
FOR i IN 1 .. 9000
LOOP
INSERT INTO random (id)
VALUES (i);
END LOOP;
COMMIT;
SELECT COUNT (*) c
INTO l_cnt
FROM random;
DBMS_OUTPUT.put_line ('-- '
|| TO_CHAR (SYSDATE, 'YYYY.MM.DD HH24:MI:SS')
|| ' count is: '
|| l_cnt);
END;
-- 2016.11.11 10:28:42 count is: 9000
Update 9000 records with random values with a single update statement
Now that we have a table of 9000 values, we can update 9000 values as requested`.
update random set value = dbms_random.value;
commit;
-- You can see those 9000 random values with a select from the table we
created for this purpose
select * from random;
Alternatives to PL/SQL for creating table records
And finally, some people have commented that the PL/SQL is bad practice for creating the values (I disagree, to me it is straightforward, and because it is procedural, easy to understand for the beginner), Here is a CTE that performs the same function. Don't forget to commit after it has finished executing.
INSERT INTO random (id)
WITH iset (num)
AS (SELECT 1
FROM DUAL
UNION ALL
SELECT num + 1
FROM iset
WHERE num < 9000)
SELECT *
FROM iset;
Another method people sometimes use is to select from all_objects. I personally don't care for this method as I believe that tables should only be used for their stated purpose. This is also defective if you need to go above the number of objects in all_objects, which on the system I am using is 82,009,
INSERT INTO random (id)
SELECT ROWNUM
FROM all_objects
WHERE ROWNUM <= 9000;
So, on the Oracle system I am creating these demonstrations on, the following will only insert 82009 rows into the table, not the requested 100000.
INSERT INTO random (id)
SELECT ROWNUM
FROM all_objects
WHERE ROWNUM <= 100000;