UPDATE statement using SUM of field

[iznubadd]

hi

i have a table READING_METER with fields READ_METER, PREVIOUS_READ and CU.

 

what i would like to do is update the value of CU field using (READ_METER - PREVIOUS_READ)

 

query:

UPDATE    READING_METER
SET  CU = SUM(READ_METER - PREVIOUS_READ)

 

when i run this i get an error on this: "An aggregate may not appear in the set list of an UPDATE statement."

 

Please help.

[corbin]

The fast way would be to do a sub query.

 

 

UPDATE READING_METER SET CU = (SELECT SUM(READ_METER-PREVIOUS_READ) FROM READING METER);