Using Rowid to tune an App-engine

Most UPDATE statements get written using the technique:

UPDATE

SET =

WHERE

However, if the value that you’re setting the field to is a fairly complex SQL statement of its own there may be a better way (particularly if you have an Oracle DB). You can take advantage of the fact that ROWID is the fastest way to locate a row (faster even than the primary key). Run the first bit of SQL to select the rowid of the row to update and the value to update it to, and then the second bit to run the updates. This can be done either as 2 SQL blocks or with an App Engine Step containing DoSelect and SQL actions.

The Select Statement

SELECT rowidtochar(rowid),

FROM

WHERE

The Update Statement

UPDATE

SET =

WHERE rowidtochar(rowid) = rowidtochar(rowid)

If you are doing this inside an App Engine, you’d need to add the rowid and value fields to the state record, and put a %Select at the start of the SELECT statement. Then you can refer to the value and the rowid in the UPDATE statement using %Bind.

Example

The Select Statement – Inside a DoSelect Action

%Select(ROWNAME1, JRNL_TOTAL_LINES, JRNL_TOTAL_DEBITS, JRNL_TOT_CREDITS)

SELECT rowidtochar(H.rowid) row_id

, (SELECT MAX(L1.JOURNAL_LINE)

FROM PS_JRNL_LN L1

WHERE L1.business_unit = h.business_unit

AND L1.journal_id = h.journal_id

AND L1.journal_date = h.journal_date

AND L1.unpost_seq = h.unpost_seq) MAX

, NVL((SELECT SUM(L2.MONETARY_AMOUNT)

FROM PS_JRNL_LN L2

WHERE L2.business_unit = h.business_unit

AND L2.journal_id = h.journal_id

AND L2.journal_date = h.journal_date

AND L2.unpost_seq = h.unpost_seq

AND L2.MONETARY_AMOUNT > 0),0) SUM_DEBITS

, NVL((SELECT SUM(L3.MONETARY_AMOUNT)

FROM PS_JRNL_LN L3

WHERE L3.business_unit = h.business_unit

AND L3.journal_id = h.journal_id

AND L3.journal_date = h.journal_date

AND L3.unpost_seq = h.unpost_seq

AND L3.MONETARY_AMOUNT <>

FROM PS_JRNL_HEADER H

WHERE (H.JOURNAL_ID LIKE 'OBAL%' OR H.JOURNAL_ID LIKE 'CBAL%')

The Update Statement – Inside a SQL Action

UPDATE PS_JRNL_HEADER

SET JRNL_TOTAL_LINES = %Bind(JRNL_TOTAL_LINES)

, JRNL_TOTAL_DEBITS = %Bind(JRNL_TOTAL_DEBITS)

, JRNL_TOT_CREDITS = %Bind(JRNL_TOT_CREDITS)

WHERE rowid = %Bind(ROWNAME1)