15.3.1.2 Modification

Modifications to the database can be done using the following functions; insert-records , delete-records and update-records . The functions commit , rollback and with-transaction are used to control transactions. Although commit or rollback may be used in isolation it is advisable to do any updates inside a with-transaction form instead. This provides consistency across different database transaction models. For example, some database systems do not provide an explicit "start-transaction" command while others do. The with-transaction form allows user code to ignore database-specific transaction models.

insert-records

Function

Inserts values for attributes (or av-pairs ) into the table into .

values

A list of values or a query expression.

av-pairs

A list of two-element lists of attributes and values.

For example:

(insert-records :into [person]

                :values

        '(114 "Joe" "Bloggs" 10000 3000 nil "plumber"))

is equivalent to the following SQL:

INSERT INTO PERSON

  VALUES (114,'Joe','Bloggs',10000,3000,NULL,'plumber')

If attributes is supplied then values must be a corresponding list of values for each of the listed attribute names. For example, both:

(insert-records :into [person]

    :attributes '(person_id income surname occupation)

    :values '(115 11000 "Johnson" "plumber"))

and:

(insert-records :into [person]

               :av-pairs `((person_id 115)

                           (income 11000)

                           (surname "Johnson")

                           (occupation "plumber")))

are equivalent to the following SQL:

INSERT INTO PERSON

  (PERSON_ID,INCOME,SURNAME,OCCUPATION)

  VALUES (115,11000,'Johnson','plumber')

If query is provided, then neither values nor av-pairs should be. In this case the attribute names in the query expression must also exist in the insertion table. For example:

(insert-records :into [person]

     :query [select [id] [firstname] [surname]

               :from [manager]]

     :attributes '(person_id firstname surname))

delete-records

Function

Deletes rows from table from where the where condition is true.

update-records

Function

Changes the values of fields in table with columns specified by attributes and values (or by av-pairs ) where the where condition is true.