Database Program Translation - Information Systems Reengineering, Integration and Normalization - page 219

These seqno columns are incremented by one for each new record. For example,
for the CLIENTACCOUNTEXECUTIVE table. The seqno is 1 and 2 for clientid
600001 (Fong et al. 2006 ).
On inserting a new record to a table, the insert trigger first finds out which col-
umn is used for counting seqno from the node_tablecolumn_mapping table. Then,
the trigger selects the maximum seqno value for the new record. The maximum
seqno value plus one will be assigned as the seqno value of the new record. For ex-
ample, a new record inserted to the table CLIENTACCOUNTEXECUTIVE on the
next page for clientid 600001 gets a new seqno value 3 since the maximum seqno
for clientid 600001 already in the table is 2.
There is no need to update the seqno value in case record is deleted. In XQL, the
location index function (e.g., position()) counts the order of the record relative to
the parent node.
Client Table

Clientid Title lastname firstname

600001 Mr Chan Peter

600002 Mrs Wong Ann

600003 Miss Lee Jane

Phone fax email seqno

27825290 27825291 [e-mail] 1

24588900 21588200 [e-mail] 1

27238900 36225555 [e-mail] 1

Clientorder table

clientid orderid Tradedate stockid Inputquantity

600001 300001 20020403 000003 10000

600002 300002 20020403 000004 10000

600003 300003 20020404 000003 20000

600003 300004 20020405 000004 6000

600002 300005 20020405 000941 6000

Action ordertype Allornothing inputdatetime Seqno

Buy Limit N 200204031001 1

Buy Limit N 200204031002 2

Sell Limit N 200204041101 1

Buy Limit N 200204051408 2

buy Limit N 200204051506 1