DELETE Statement

Syntax 

DELETE FROM table_identifier USING {stream_identifier | stream_expression}
  WHERE predicate
  [RETURNING target_list]
  [ERROR INTO stream_identifier];

Substitutable Fields

table_identifier

The unique identifier (name) of the table from which to delete rows.

stream_identifier

The unique identifier (name) of the stream whose tuples contain the values that will be used to delete rows from the table.

stream_expression

A StreamSQL statement that produces a stream whose tuples contain the values that will be used to delete rows from the table. The statement must be enclosed within parentheses.

predicate

The logic used to select specific table content.

target_list

One or more entries, separated by commas, of the format target_list_entry.

target_list_entry

A value, of the format scalar_expression [AS output_field_identifier], to be included in the result set returned by the statement.

scalar_expression

An expression that generates a value for a tuple field that is returned by the delete operation. Values can be obtained from an input tuple field, from a simple function or from the table. Optionally, the name for a value can be modified through an AS clause.

output_field_identifier

A unique identifier (name) for the tuple field that contains a value returned by the delete operation.

ERROR INTO Clause

You can append an ERROR INTO clause just before the closing semicolon. The StreamSQL ERROR INTO clause is analogous to the Enable Error Output Port check box for operators and adapters in EventFlow applications.

Use ERROR INTO with the name of a stream, which must already exist. This sets up an Error Port for this operator, which is much like a local catch mechanism for errors from this operator.

See Using Error Ports and Error Streams for a discussion of StreamBase error handling mechanisms.

Discussion

The DELETE statement removes a row, or rows, from an existing table.

With the DELETE statement, the USING clause identifies the stream whose tuples contain the values that will be used to identify the rows that will be deleted from the table. Since multiple rows can be deleted, the optional ORDER BY [DESC] LIMIT number clause provides a way to limit the number of rows affected and to organize the result set generated by the RETURNING clause.

In the RETURNING clause, scalar_expression can specify a value from the stream and/or from the table. For example: 

DELETE ...
  RETURNING tuple_field_identifier [AS ...][, ...], column_identifier [AS ...][, ...]

The result set generated by the RETURNING clause must be captured into a stream. You can use the CREATE STREAM statement to define a stream and the INTO keyword to populate the stream with the content generated by the RETURNING clause. As an alternative, in a single statement use the => (arrow) operator with a CREATE STREAM statement, as illustrated below. 

CREATE STREAM stream_identifier;
DELETE ... RETURNING ... INTO stream_identifier;

Or 

DELETE ... RETURNING ... => CREATE STREAM stream_identifier

Related Topics

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