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     DECLARE(l)	  SQL - Language Statements (2002-11-22)    DECLARE(l)

     NAME
	  DECLARE - define a cursor

     SYNOPSIS
	  DECLARE cursorname [ BINARY ] [ INSENSITIVE ] [ SCROLL ]
	      CURSOR FOR query
	      [ FOR { READ ONLY | UPDATE [ OF column [, ...] ] ]

	INPUTS
	  cursorname
	       The name of the cursor to be used in subsequent FETCH
	       operations.

	  BINARY
	       Causes the cursor to fetch data in binary rather than
	       in text format.

	  INSENSITIVE
	       SQL92 keyword indicating that data retrieved from the
	       cursor should be unaffected by updates from other
	       processes or cursors.  Since cursor operations occur
	       within transactions in PostgreSQL this is always the
	       case.  This keyword has no effect.

	  SCROLL
	       SQL92 keyword indicating that data may be retrieved in
	       multiple rows per FETCH operation. Since this is
	       allowed at all times by PostgreSQL this keyword has no
	       effect.

	  query
	       An SQL query which will provide the rows to be governed
	       by the cursor.  Refer to the SELECT statement for
	       further information about valid arguments.

	  READ ONLY
	       SQL92 keyword indicating that the cursor will be used
	       in a read only mode. Since this is the only cursor
	       access mode available in PostgreSQL this keyword has no
	       effect.

	  UPDATE
	       SQL92 keyword indicating that the cursor will be used
	       to update tables. Since cursor updates are not
	       currently supported in PostgreSQL this keyword provokes
	       an informational error message.

	  column
	       Column(s) to be updated.	 Since cursor updates are not
	       currently supported in PostgreSQL the UPDATE clause

     Page 1					     (printed 3/24/03)

     DECLARE(l)	  SQL - Language Statements (2002-11-22)    DECLARE(l)

	       provokes an informational error message.

	OUTPUTS
	  DECLARE CURSOR
	       The message returned if the SELECT is run successfully.

	  WARNING: Closing pre-existing portal "cursorname"
	       This message is reported if the same cursor name was
	       already declared in the current transaction block. The
	       previous definition is discarded.

     blocks
	  ERROR: DECLARE CURSOR may only be used in begin/end transaction
	       This error occurs if the cursor is not declared within
	       a transaction block.

     DESCRIPTION
	  DECLARE allows a user to create cursors, which can be used
	  to retrieve a small number of rows at a time out of a larger
	  query. Cursors can return data either in text or in binary
	  format using FETCH [fetch(l)].

	  Normal cursors return data in text format, either ASCII or
	  another encoding scheme depending on how the PostgreSQL
	  backend was built. Since data is stored natively in binary
	  format, the system must do a conversion to produce the text
	  format. In addition, text formats are often larger in size
	  than the corresponding binary format.	 Once the information
	  comes back in text form, the client application may need to
	  convert it to a binary format to manipulate it.  BINARY
	  cursors give you back the data in the native binary
	  representation.

	  As an example, if a query returns a value of one from an
	  integer column, you would get a string of 1 with a default
	  cursor whereas with a binary cursor you would get a 4-byte
	  value equal to control-A (^A).

	  BINARY cursors should be used carefully. User applications
	  such as psql are not aware of binary cursors and expect data
	  to come back in a text format.

	  String representation is architecture-neutral whereas binary
	  representation can differ between different machine
	  architectures.  PostgreSQL does not resolve byte ordering or
	  representation issues for binary cursors.  Therefore, if
	  your client machine and server machine use different
	  representations (e.g., ``big-endian'' versus ``little-
	  endian''), you will probably not want your data returned in
	  binary format.  However, binary cursors may be a little more
	  efficient since there is less conversion overhead in the
	  server to client data transfer.

     Page 2					     (printed 3/24/03)

     DECLARE(l)	  SQL - Language Statements (2002-11-22)    DECLARE(l)

	       Tip: If you intend to display the data in ASCII,
	       getting it back in ASCII will save you some effort on
	       the client side.

	NOTES
	  Cursors are only available in transactions. Use to BEGIN
	  [begin(l)], COMMIT [commit(l)] and ROLLBACK [rollback(l)] to
	  define a transaction block.

	  In SQL92 cursors are only available in embedded SQL (ESQL)
	  applications. The PostgreSQL backend does not implement an
	  explicit OPEN cursor statement; a cursor is considered to be
	  open when it is declared.  However, ecpg, the embedded SQL
	  preprocessor for PostgreSQL, supports the SQL92 cursor
	  conventions, including those involving DECLARE and OPEN
	  statements.

     USAGE
	  To declare a cursor:

	  DECLARE liahona CURSOR
	      FOR SELECT * FROM films;

     COMPATIBILITY
	SQL92
	  SQL92 allows cursors only in embedded SQL and in modules.
	  PostgreSQL permits cursors to be used interactively.	SQL92
	  allows embedded or modular cursors to update database
	  information.	All PostgreSQL cursors are read only.  The
	  BINARY keyword is a PostgreSQL extension.

     Page 3					     (printed 3/24/03)

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