mysql - Assigning a value from another database and function - MySQL variable scope

Question

I am using MySQL to make a report showing the number of hours billed for a particular date range and project. The complexity is that the date range is variable for each project (different start month and start day). This information is coming from a value in another database/table.

I have the following UDF in MySQL:

DELIMITER //

CREATE FUNCTION TimeLeft(startday INT, today INT) RETURNS INT
DETERMINISTIC
BEGIN
DECLARE s INT;
   IF startday < today THEN SET s = 0;
     ELSE SET s = 1;
     END IF;
   RETURN s;
END //

DELIMITER; 

I use that function in the following query, which is supposed to take the value returned in the TimeLeft function to determine the values for the start month (month(curdate())-@xx) and start day (@yy) for each project to calculate the hours:

AND time_records.record_date >= concat('2012/', month(curdate())-@xx , '/' , @yy)  

Here's how I am setting the values for @xx and @yy:

SET @xx = 0; #this is the value that we will use to manipulate the month for the date range
SET @yy = 0;
@yy:= SELECT start_day_of_month FROM dashboard.client; #this doesn't seem to work
SELECT @xx:= TimeLeft(@yy,dayofmonth(curdate()));

I am getting some issues:

1. @yy is not getting the value - possibly my syntax is wrong?
2. The variables are set at the top of the code, so they are not getting changed for each project as they should be (there should be a different @xx and @yy for each project since each one has a different start and end date).

Here's the full query:

#below is where I assign the variables

SET @xx = 0; #this is the value that we will use to manipulate the month for the date range
SET @yy = 0;
@yy:= SELECT start_day_of_month FROM dashboard.client; #this doesn't seem to work
SELECT @xx:= TimeLeft(@yy,dayofmonth(curdate()));


# below is the MySQL query that is meant to use the variables assigned above

SELECT X.expr1 AS 'Project Name', @monthly_hours - SUM(X.expr2) AS 'Hours Billed
FROM 
  (SELECT 
    projects.name AS expr1
    , sum(time_records.value) AS expr2
  FROM project_objects
  INNER JOIN projects
    ON projects.id = project_objects.project_id
  INNER JOIN time_records
    ON time_records.parent_id = project_objects.id
  WHERE time_records.parent_type = 'Task' 
  AND time_records.record_date >= concat('2012/', month(curdate())-@xx , '/' , @yy)  
  AND time_records.record_date <= curdate()
  GROUP BY projects.name

  UNION

  SELECT 
    projects.name AS expr1
    , sum(time_records.value) as expr2
  FROM projects
  INNER JOIN time_records
    ON projects.id = time_records.parent_id
  WHERE time_records.parent_type = 'Project'
  AND time_records.record_date >= concat('2012/', month(curdate())-@xx , '/' , @yy)     
  AND time_records.record_date <= curdate() 
  GROUP BY projects.name) X
GROUP BY X.expr1

I think there is some issue of where I am assigning the variables @xx and @yy. These should be done for each individual Project, so putting them up on the top is probably not the best idea. I'm also not sure if I am assigning the @yy value correctly. It's supposed to query the value of the field of a table that is in another database but it keeps throwing a syntax error on the @yy assignment to that field.

Answer 1

@yy内部に値を割り当てますselect：

SELECT @yy:= start_day_of_month FROM dashboard.client;