Thread: Order of Operations for Update Command
The following documentation comment has been logged on the website: Page: https://www.postgresql.org/docs/9.5/static/sql-update.html Description: Does the Update command update the columns in the order they are listed? Can an updated column's new value be used in the value calculation for a subsequent column? i.e. update mytable set qty=qty+5,price=price*1.1,subtotal=qty*price Will the subtotal be calculated based on the old column values or the new column values?
simonwhite@dciphercomputing.com writes: > Does the Update command update the columns in the order they are listed? Notionally, they're all done concurrently. This is embodied in our docs by defining the update source expressions thus: An expression to assign to the column. The expression can use the old values of this and other columns in the table. > Can an updated column's new value be used in the value calculation for a > subsequent column? No, see above. regards, tom lane