Phantom Rows in SQL Server

This situation comes when we are doing simultaneous INSERT, UPDATE and DELETE on a table.

Let suppose we have a table with structure
STUDENT (Roll, Name, Marks, Grade)

Now two person at the same time say Peter and Jim trying to UPDATE and INSERT data respectively.

Peter:

UPDATE STUDENT

SET
Grade = ‘A’

WHERE

Marks = 90

Jim:

INSERT INTO STUDENT

(Roll, Name, Marks)

VALUES

(11,’Sam’, 90)

This situation is called phantom rows.

Due to concurrency this particular record will not get affected.