sql -- select and update - mysql

Question

I've being trying to amend the solution found in this tutorial to write an SQL query that both SELECTs and UPDATEs my table:
enter link description here
DECLARE #column1 varchar(2);
SET #column1 = (SELECT `Id`, `Url` FROM `MyTable` WHERE `Retrieved` = 0);
SELECT * FROM `MyTable` WHERE `AdId`, `Url` = #column1;
UPDATE `MyTable` SET `Retrieved` = 1 where `Id`, `Url` = #column1;
What i'm trying to achieve the following simultaneously:
SELECT Id, Url FROM MyTable WHERE Retrieved = 0
UPDATE MyTable SET Retrieved = 1
for the rows where i have SELECTed the results from
Basically, i want to select all data from ID and Url columns where the Retrieved column equals 0. I then want to set the Retrieved column to 1 for the rows i have selected.

Answer 1

The "normal" SQL method would be:
UPDATE MyTable
SET Retrieved = 1
WHERE id IN (SELECT Id FROM MyTable WHERE Retrieved = 0);
That does not work in MySQL. Assuming that id is unique in MyTable (a reasonable assumption in my opinion), then this does what you want:
UPDATE MyTable
SET Retrieved = 1
WHERE Retrieved = 0;

Answer 2

UPDATE t SET t.Retrieved=1 FROM MyTable t WHERE t.Retrieved=0
This is only updating rows, that essentially you've selected. In your case you want to update rows where the selected rows Retrieved column is equal to 0.
The other thing and maybe for readibility or you need the rows returned you can use a cte.
--first get only the records you need
WITH MyRecords_cte
AS
(
SELECT Id, URL, Retreived FROM MyTable WHERE Retreived=0
)
UPDATE MyRecords_cte SET MyRecords_cte.Retreived=1
Once you're done with the update you can return the data.