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[Gold <1967811@xxxxxxxxxxxxxxxxxx>]

Bob spotted that MySQL has some weird behaviour when it comes to reading
and writing to the same table.  This method gets around that though;

        execute_sql("
            UPDATE {group}
            SET submittableto = 1
            WHERE id IN ((
                SELECT foo.id FROM (
                    SELECT g1.id
                    FROM {lti_assessment} l
                    JOIN {group} g1 ON g1.id = l.group
                    WHERE g1.submittableto = 0
                ) AS foo
            ));");

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https://bugs.launchpad.net/bugs/1967811

Title:
  SQL vs MySQL on group table update

Status in Mahara:
  New

Bug description:
  I was switching DBs for ES7 testing on a smaller dataset. The smaller db is on MySQL.  During the site upgrade I got this:
  ```
  [DBG] 66 (lib/dml.php:180) mysqli error: [1093: You can't specify target table 'group' for update in FROM clause] in EXECUTE("
              UPDATE "group" SET submittableto = 1 WHERE id IN (
                  SELECT g1.id FROM "lti_assessment" l
                  JOIN "group" g1 ON g1.id = l.group
                  WHERE g1.submittableto = 0
              )")Command was:
              UPDATE "group" SET submittableto = 1 WHERE id IN (
                  SELECT g1.id FROM "lti_assessment" l
                  JOIN "group" g1 ON g1.id = l.group
                  WHERE g1.submittableto = 0
              )
  ```

  This is related to this review:
  https://reviews.mahara.org/c/mahara/+/12492

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