The PREVIOUS function is relevant only for interrow calculations. It can be used only in the model_clause of the SELECT statement and then only in the ITERATE ... [ UNTIL ] clause of the model_rules_clause. It returns the value of cell_reference at the beginning of each iteration.

See Also:

model_clause and "Model Expressions" for the syntax and semantics of interrow calculations

Examples

The following example repeats the rules, up to 1000 times, until the difference between the values of cur_val at the beginning and at the end of an iteration is less than one:

SELECT dim_col, cur_val, num_of_iterations
  FROM (SELECT 1 AS dim_col, 10 AS cur_val FROM dual)
  MODEL
    DIMENSION BY (dim_col)
    MEASURES (cur_val, 0 num_of_iterations)
    IGNORE NAV
    UNIQUE DIMENSION
    RULES ITERATE (1000) UNTIL (PREVIOUS(cur_val[1]) - cur_val[1] < 1)
    (
      cur_val[1] = cur_val[1]/2,
      num_of_iterations[1] = num_of_iterations[1] + 1
    );

   DIM_COL    CUR_VAL NUM_OF_ITERATIONS
---------- ---------- -----------------
         1       .625                 4