Can't figure out this error near FROM statement in TRIGGER-CodePudding

This is probably a stupid mistake but I can't figure out what causes the error. I'm trying to compare the sum of Employee cost in one plan to the budget of the project before each insert. This is for sqlite, thanks for any answers in advance.

%%sql
CREATE TRIGGER trg_ins_PlanEmployees BEFORE INSERT ON PlanEmployees
BEGIN 
    SELECT
        CASE
            WHEN NOT EXISTS (
                SELECT 1
                FROM Project pro
                INNER JOIN Plan ON pro.projectID = Plan.projectID
                INNER JOIN PlanEmployees ON Plan.pID = PlanEmployees.pID
                INNER JOIN Employee ON PlanEmployee.eID = Employee.eID
                WHERE SUM(cost) FROM Employee <= project.budget
            )
            THEN RAISE (ABORT, 'Over budget')
        END;
END;

CodePudding user response：

The query of

            SELECT 1
            FROM Project pro
            INNER JOIN Plan ON pro.projectID = Plan.projectID
            INNER JOIN PlanEmployees ON Plan.pID = PlanEmployees.pID
            INNER JOIN Employee ON PlanEmployee.eID = Employee.eID
            WHERE SUM(cost) FROM Employee <= project.budget

is syntactically incorrect because of the

WHERE SUM(cost) FROM Employee <= project.budget

part, because SUM is an aggregate function that does not evaluate to boolean and is incorrect by itself to form the where clause and the FROM cannot be defined twice, nor after the WHERE.

Possible fix:

            SELECT 1
            FROM Project pro
            INNER JOIN Plan ON pro.projectID = Plan.projectID
            INNER JOIN PlanEmployees ON Plan.pID = PlanEmployees.pID
            INNER JOIN Employee ON PlanEmployee.eID = Employee.eID
            WHERE SUM(cost) <= project.budget