UNIQUE clause   When a cursor is declared UNIQUE, the query is forced to return all the columns required to uniquely identify each row. Often this means ensuring that all columns in the primary key or a uniqueness table constraint are returned. Any columns that are required but were not specified in the query are added to the result set.

A DESCRIBE done on a UNIQUE cursor sets the following additional options in the indicator variables:

NO SCROLL clause   A cursor declared NO SCROLL is restricted to moving forward through the result set using FETCH NEXT and FETCH RELATIVE 0 seek operations.

As rows cannot be returned to once the cursor leaves the row, there are no sensitivity restrictions on the cursor. When a NO SCROLL cursor is requested, SQL Anywhere supplies the most efficient kind of cursor, which is an asensitive cursor.

DYNAMIC SCROLL clause   DYNAMIC SCROLL is the default cursor type. DYNAMIC SCROLL cursors can use all formats of the FETCH statement.

When a DYNAMIC SCROLL cursor is requested, SQL Anywhere supplies an asensitive cursor. When using cursors there is always a trade-off between efficiency and consistency. Asensitive cursors provide efficient performance at the expense of consistency.

SCROLL clause   A cursor declared SCROLL can use all formats of the FETCH statement. When a SCROLL cursor is requested, SQL Anywhere supplies a value-sensitive cursor. With a value-sensitive cursor, a subsequent FETCH of a previously FETCHed result row may return a warning or an error if the underlying row has been modified or deleted.

SQL Anywhere must execute value-sensitive cursors in such a way that result set membership is guaranteed. DYNAMIC SCROLL cursors are more efficient and should be used unless the consistent behavior of SCROLL cursors is required.

INSENSITIVE clause   A cursor declared INSENSITIVE has its membership fixed when it is opened; a temporary table is created with a copy of all the original rows. FETCHING from an INSENSITIVE cursor does not see the effect of any other INSERT, UPDATE, or DELETE statement from concurrently-executing transactions, or any other update operations from within the same transaction. INSENSITIVE cursors are not updatable.

SENSITIVE clause   A cursor declared SENSITIVE is sensitive to changes to membership or values of the result set.

FOR statement-name clause   Statements are named using the PREPARE statement. Cursors can be declared only for a prepared SELECT or CALL. The cursor updatability specified in the PREPARE statement is used for the cursor, unless the SQL preprocessor -m HISTORICAL option is specified.

USING variable-name clause   For use within stored procedures only. The variable is a string containing a SELECT statement for the cursor. The variable must be available when the DECLARE is processed, and so must be one of the following:

A parameter to the procedure. For example:

CREATE FUNCTION GetRowCount( IN qry LONG VARCHAR )
RETURNS INT
BEGIN
  DECLARE crsr CURSOR USING qry;
  DECLARE rowcnt INT;

  SET rowcnt = 0;
  OPEN crsr;
  lp: LOOP
    FETCH crsr;
    IF SQLCODE <> 0 THEN LEAVE lp END IF;
    SET rowcnt = rowcnt + 1;
  END LOOP;
  CLOSE crsr;
  RETURN rowcnt;
END;

Nested inside another BEGIN...END after the variable has been assigned a value. For example:

CREATE PROCEDURE get_table_name(
  IN id_value INT, OUT tabname CHAR(128)
)
BEGIN
  DECLARE qry LONG VARCHAR;

  SET qry = 'SELECT table_name FROM SYS.SYSTAB ' ||
            'WHERE table_id=' || string(id_value);
  BEGIN
    DECLARE crsr CURSOR USING qry;
    OPEN crsr;
    FETCH crsr INTO tabname;
    CLOSE crsr;
  END
END;