Although chained mode implicitly begins transactions with data retrieval or modification statements, you can nest transactions only by explicitly using begin transaction statements. Once the first transaction implicitly begins, further data retrieval or modification statements no longer begin transactions until after the first transaction commits or aborts. For example, in the following query, the first commit transaction commits all changes in chained mode; the second commit is unnecessary:
insert into publishers
values ("9907", null, null, null)
insert into publishers
values ("9908", null, null, null)
commit transaction
commit transaction
In chained mode, a data retrieval
or modification statement begins a transaction whether or not it
executes successfully. Even a select that does
not access a table begins a transaction.
