Question

I have an assignment table in my database. I also have a assignment_notes table, which has a reference to the assignment table. There can exists multiple rows in this table.

When I select all my assignments, I want to check if there exists some notes to this assignment. And all I want is a true/false return.

Is it possible to do something like (pseudo):

Select all assignments; if assignment
has assignment_notes HasNotes = true; else
HasNotes = false.

I hope I made this clear enough – I’m not so good at explaining programming stuff 😉

Answer 1

DECLARE @Assignments TABLE
(
    Id INT NOT NULL IDENTITY(1,1) PRIMARY KEY,
    Name VARCHAR(30) NOT NULL
)

DECLARE @AssignmentNotes TABLE
(
    Id INT NOT NULL IDENTITY(1,1) PRIMARY KEY,
    AssignmentId INT NOT NULL,
    Note VARCHAR(MAX)
)

INSERT INTO @Assignments(Name) VALUES('Biology')
INSERT INTO @Assignments(Name) VALUES('Chemistry')

INSERT INTO @AssignmentNotes (AssignmentId, Note) VALUES(1, 'Studies on DNA')
INSERT INTO @AssignmentNotes (AssignmentId, Note) VALUES(1, 'Evolution notes from Darwin')

SELECT
    A.*,
    CASE WHEN COUNT(AN.Id) > 0 THEN 1 ELSE 0 END AS HasNotes    
FROM    
    @Assignments AS A
    LEFT JOIN
    @AssignmentNotes AS AN
    ON A.Id = AN.AssignmentId
GROUP BY
    A.Id,
    A.Name