SQL INSERT, UPDATE, and DELETE Commands
The SQL INSERT, UPDATE, and DELETE commands
enable SQL users to manipulate and modify data:
- The INSERT statement introduces new
rows into an existing table.
- The DELETE statement removes a row or
combination of rows from a table.
- The UPDATE statement enables users to
update a row or group of rows in a table.
You can issue an SQL INSERT, UPDATE,
or DELETE command against one segment instance (row) at a time.
When you issue one of these commands against a multi-segment Master File:
- All fields referenced in the command
must be on a single path through the file structure.
- The command
must explicitly specify (in the WHERE predicate) every key value
from the root to the target segment instance, and this combination
of key values must uniquely identify one segment instance (row)
to be affected by the command.
If you are modifying every field
in the row, you can omit the list of field names from the command.
- The SQL Translator
supports subqueries, such as:
Although each INSERT, UPDATE, or DELETE
command can specify only one row, referential integrity constraints
may produce the following modifications to the data source:
- If you delete
a segment instance that has descendant segment instances (children),
the children are automatically deleted.
- If you insert
a segment for which parent segments are missing, the parent segments are