Question

I am trying to figure out if I can do some math completely within mySQL (5.1) but am not
sure if this is possible. I am not an expert with SQL.

I have two tables. One to track overall time, and one with individiual time entries.
The idea is to keep a running total in Table1 based on what was used in Table2.

Table1:

UserID (INT),
TotalTime (INT)

Table2:

UserID (INT),
TimeUsed (INT),
isCalculated (bool)

What I would like to do is iterate through Table 2 where isCalculated is false and
subtract the Table2.TimeUsed for each entry from the Table1.TotalTime where Table1.UserID=Table2.UserID.

After the calculation I would need to toggle isCalculated to true.

It seems this could be done in a loop, but I am not sure of the proper syntax in mySQL.

Thanks for any guidance.

Answer 1

UPDATE
    Table1
    JOIN Table2 ON Table1.UserID = Table2.UserID
SET
    Table1.TotalTime = Table1.TotalTime - Table2.TimeUsed,
    Table2.isCalculated = TRUE
WHERE
    NOT Table2.isCalculated