Transactions: Case Study Scenario C

Time

Renata

Lillian

0

INSERT INTO Students VALUES

(‘colton@email.com’, ‘Colton', 85);

1

SELECT * FROM Students;

2

INSERT INTO Students VALUES

(‘david@email.com’, ‘David’, 64);

Which result (see Transactions: Case Study Intro) would you expect to see if you were Lillian, when she runs the query?

Question

Transactions: Case Study Scenario C

Time

Renata

Lillian

0

INSERT INTO Students VALUES

(‘colton@email.com’, ‘Colton', 85);

1

SELECT * FROM Students;

2

INSERT INTO Students VALUES

(‘david@email.com’, ‘David’, 64);

Which result (see Transactions: Case Study Intro) would you expect to see if you were Lillian, when she runs the query?

BlackTom AI · Accepted Answer

Let’s walk through what happens step by step when Lillian runs the query.
Option 1: 'Result #1: 0 rows returned' would imply that the Students table is empty at the moment of the query. Since there is an INSERT at time 0 that adds Colton's row before the SELECT at time 1, the table is not empty at that moment. Therefore, this option contradicts the sequence of operations provided.
Option 2: 'Result #2: 2 rows returned' would mean there are two rows in the table when the SELECT executes at time 1. We only see one INSERT occurred prior to the SELECT (the Colton row). The second INSERT happens later, at time 2, after the SELECT. Thus, two rows at time 1 would be incorrect given the described timing.
Option 3: 'Result #3: 3 rows returned' would indicate three rows are present at the moment of the SELECT. That would require more rows to have been inserted before time 1 than shown in the scenario, or that some extra rows exist initially. Based on the explicit timeline, this seems unlikely unless there was pre-existing data not described in the scenario.
Option 4: 'Result #4: 4 rows returned' would imply four rows present at time 1, which again cannot be explained by the two inserts shown (one at time 0 and one later at time 2) because the second insert happens after the query, not before it.
A key point to emphasize is the ordering of operations: the SELECT occurs after the first INSERT and before the second INSERT. Therefore, the number of rows visible at the time of the SELECT should reflect only the inserts that occurred up to that moment. If the scenario strictly follows the times shown, you would expect the number of rows to correspond to the single insertion already made prior to the SELECT, i.e., one row. If the answer choices do not include '1 row', that signals a mismatch between the described sequence and the options given.
Additionally, note that the content of the row (Colton’s data) does not affect the count of rows returned by the query; the count is about how many rows exist, not what their values are. Misconceptions to watch for include assuming that the second INSERT has already occurred (which would double-count after time 2) or assuming that the SELECT returns metadata instead of actual data rows.
In summary, evaluating the timing shows that the number of rows at the moment of the SELECT should reflect only the inserts that happened before that moment. The provided options present counts that are inconsistent with the stated sequence unless there is extra, unmentioned data at the start or a different interpretation of the time markers.

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