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 )