Question

I’m currently using the following query to determine which projects in a database have no associated milestones:

SELECT P.project_id, COUNT(M.milestone_id) as count FROM projects P
LEFT JOIN milestones M USING(project_id)
GROUP BY P.project_id
HAVING count < 1

and it returns:

project   count
---------------
9         0
34        0
32        0
41        0

How do I now go INSERT a new milestone row for each project_id in that table?

Answer 1

You can use the INSERT...SELECT statement

INSERT INTO tableName (project_ID)
SELECT  P.project_id
FROM    projects P
            LEFT JOIN milestones M 
                USING(project_id)
GROUP BY P.project_id
HAVING count < 1

change tableNAme to the name of the table where you want to insert the new row/s.

UPDATE 1

INSERT INTO tableName (project_ID, colA, colB, colC)
SELECT  P.project_id, colA, colB, colC
FROM    projects P
            LEFT JOIN milestones M 
                USING(project_id)
GROUP BY P.project_id
HAVING count < 1

now question arises, what if you want to have a value which is not present in the column? you can create virtual values for that.

INSERT INTO tableName (project_ID, field1, field2, field3)
SELECT  P.project_id, '' AS field1, 0 AS field2, NULL AS field3
FROM    projects P
            LEFT JOIN milestones M 
                USING(project_id)
GROUP BY P.project_id
HAVING count < 1