DD_UPDATE（更新策略组件的一种方式）
Flags records for update in an update strategy expression. DD_UPDATE is equivalent to the?
?
integer literal 1.
Note: Use the DD_UPDATE constant in the Update Strategy transformation only. Use DD_UPDATE?
?
instead of the integer literal 1 to facilitate troubleshooting complex numeric expressions.
When you run a workflow, select the data-driven update strategy to write records to a target?
?
based on this flag.
Examples
?
The following examples modify a mapping that calculates sales for the current month. The?
?
mapping loads sales for one employee.
?
This expression flags records for Alex as updates and flags all others for rejection:
IIF( EMPLOYEE.NAME = 'Alex', DD_UPDATE, DD_REJECT )
This expression uses numeric literals to produce the same result, flagging Alex’s sales for?
?
update (1) and flagging all other sales records for rejection (3):
IIF( EMPLOYEE.NAME = 'Alex', 1, 3 )
Notice that the expression using constants is easier to read than the expression using?
?
numeric literals.
The following update strategy expression uses SYSDATE to find only those orders that have?
?
shipped in the last two days and flag them for insertion. Using DATE_DIFF, the expression?
?
subtracts DATE_SHIPPED from the system date, returning the difference between the two dates.?
?
Because DATE_DIFF returns a Double value, the expression uses TRUNC to truncate the?
?
difference. It then compares the result to the integer literal 2. If the result is greater?
?
than 2, the expression flags the records for rejection. If the result is 2 or less, it flags?
?
the records for update. Otherwise, it flags them for rejection:
IIF( TRUNC( DATE_DIFF( SYSDATE, ORDERS.DATE_SHIPPED, 'DD' ), 0 ) > 2, DD_REJECT, DD_UPDATE )
