Oracle9i SQL Reference
Release 1 (9.0.1)

Part Number A90125-01
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Functions, 164 of 166


WIDTH_BUCKET

Syntax

width_bucket::=


Text description of functions80a.gif follows
Text description of width_bucket

Purpose

The WIDTH_BUCKET function lets you construct equiwidth histograms, in which the histogram range is divided into intervals that have identical size. (Compare this function with NTILE, which creates equiheight histograms.) Ideally each bucket is a "closed-open" interval of the real number line. For example, a bucket can be assigned to scores between 10.00 and 19.999... to indicate that 10 is included in the interval and 20 is excluded. This is sometimes denoted [10, 20).

For a given expression, WIDTH_BUCKET returns the bucket number into which the value of this expression would fall after being evaluated.

Oracle also creates (when needed) an underflow bucket numbered 0 and an overflow bucket numbered num_buckets+1. These buckets handle values less than min_value and more than max_value and are helpful in checking the reasonableness of endpoints.

Example

The following example creates a ten-bucket histogram on the credit_limit column for customers in Switzerland in the sample table oe.customers and returns the bucket number ("Credit Group") for each customer. Customers with credit limits above the maximum value are assigned to the overflow bucket, 11:

SELECT customer_id, cust_last_name, credit_limit, 
   WIDTH_BUCKET(credit_limit, 100, 5000, 10) "Credit Group"
   FROM customers WHERE nls_territory = 'SWITZERLAND'
   ORDER BY "Credit Group";

CUSTOMER_ID CUST_LAST_NAME       CREDIT_LIMIT Credit Group
----------- -------------------- ------------ ------------
        825 Dreyfuss                      500            1
        826 Barkin                        500            1
        853 Palin                         400            1
        827 Siegel                        500            1
        843 Oates                         700            2
        844 Julius                        700            2
        835 Eastwood                     1200            3
        840 Elliott                      1400            3
        842 Stern                        1400            3
        841 Boyer                        1400            3
        837 Stanton                      1200            3
        836 Berenger                     1200            3
        848 Olmos                        1800            4
        849 Kaurusmdki                   1800            4
        828 Minnelli                     2300            5
        829 Hunter                       2300            5
        852 Tanner                       2300            5
        851 Brown                        2300            5
        850 Finney                       2300            5
        830 Dutt                         3500            7
        831 Bel Geddes                   3500            7
        832 Spacek                       3500            7
        838 Nicholson                    3500            7
        839 Johnson                      3500            7
        833 Moranis                      3500            7
        834 Idle                         3500            7
        845 Fawcett                      5000           11
        846 Brando                       5000           11
        847 Streep                       5000           11

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