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SQL Query to extract tasks with subtasks [duplicate]

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Hi I'm new to MySQL and working on a small project.

I've got 3 tables:

+-------------+ +--------------+ +--------------+
| Project | | Task | | Subtask |
+-------------+ +--------------+ +--------------+
| Pname | | Tname | | Sname |
+-------------+ | pname (FK) | | Tname (FK) |
+--------------+ | pname (FK) |
+--------------+


I need an SQL query to display all the tasks along with their subtasks that belong to a particular project. In the form (task, subtask)
If a task doesn't have a subtask then it's corresponding entry should be NULL.
I know this is stupid but here's what I tried,

tasks

subtasks

task

subtask

task

SELECT Tname, Sname from Task, Subtask WHERE pname='some project'


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1 Answer
1

What you need is a LEFT JOIN so that you will still get tasks which have no sub-tasks. Try this:

LEFT JOIN

SELECT T.Tname, S.Sname
FROM Task T
LEFT JOIN Subtask S ON S.TName = T.TName
WHERE T.PName = 'some project'