Database Program Translation - Information Systems Reengineering, Integration and Normalization - page 215

By following the algorithm delete, we can translate the SQL statement to the fol-
lowing OSQL statements by deleting the aggregate attribute of the composite ob-
jects that contain the to-be-deleted object, and also by deleting the set of OFFICE
that John Doe occupies, and then delete the to-be-deleted object with the aggregate
objects pointing to the composite objects as:

6(/(&7 3 GHSDUWPHQW 3 RIILFH IURP 67$))ZKHUH 66
LQWR2,' VWDII
83'$7('(3$570(17VHW3 VWDII 3 VWDII 2,' VWDII
83'$7(2)),&(VHW3 RFFXSDQW 3 RFFXSDQW ^2,' VWDII `
'(/(7($//IURP3(5621ZKHUH66

Now, suppose John Doe actually wants to transfer from the CS department to the IS
department. The SQL for the update statement is:
UPDATE STAFF set dept-name = 'IS' where SS# = 452112345
By following the algorithm update, we can translate the SQL statement to sets of
OSQL statements as:

6(/(&73 RIILFH IURP67$))ZKHUH66 LQWR2,' VWDII
83'$7('(3$570(17VHW3 VWDII 3 VWDII 2,' VWDII ZKHUH'HS ´&6´
83'$7(2)),&(VHW3 VWDII 3 VWDII ^2,' VWDII `ZKHUH'HS ´&6´
83'$7('(3$570(17VHW3 VWDII 3 VWDII 2,' VWDII ZKHUH'HS ´,6´
83'$7(2)),&(VHW3 VWDII 3 VWDII ^2,' VWDII `ZKHUH'HS ´,6´
83'$7(67$))VHWGHSWQDPH µ,6¶ZKHUH66

5.11 Query Translation from SQL to XQL

An XML Query Language (XQL) is a query language for XML documents, and
can be implemented by XPath. The SQL allows data retrieval using table join and
data manipulation using methods. In query transformation, a syntax-directed parser
converts the SQL into multi-way trees. The transformation process is performed,
based on the subtree matching and replacement technique. The process of SQL
query transformation is given in Fig. 5.13 .

5.11.1 Translation of SQL Query to XPath Query

After the schema is done, SQL query can be translated to XPath query by the fol-
lowing steps:

1. Decompose SQL query transaction