How to do histograms in PostgreSQL

SELECT * FROM histogram($table_name_or_subquery, $column_name);

. . . to give sweet results like this, in a check of the distribution of 2016 political contributions in Vermont:

fec=# SELECT * FROM histogram('(SELECT * FROM small_donors_vt LIMIT 50000)', 'transaction_amt');

 bucket |   range   | freq |       bar       
--------+-----------+------+-----------------
      1 | [0,9]     | 2744 | ******
      2 | [10,19]   | 5630 | *************
      3 | [20,29]   | 6383 | ***************
      4 | [30,39]   | 1290 | ***
      5 | [40,49]   |  369 | *
      6 | [50,59]   | 3541 | ********
      7 | [60,69]   |  174 | 
      8 | [70,79]   |  313 | *
      9 | [80,89]   |  171 | 
     10 | [90,99]   |   65 | 
     11 | [100,109] | 2363 | ******
     12 | [110,119] |   51 | 
     13 | [120,129] |  115 | 
     14 | [130,139] |   32 | 
     15 | [140,146] |   11 | 
     16 | [150,159] |  187 | 
     17 | [160,169] |   24 | 
     18 | [170,177] |   33 | 
     19 | [180,189] |   19 | 
     20 | [191,199] |   24 | 
     21 | [200,200] |  795 | **

PostgreSQL, Aggregates and Histograms

Let’s have a look at our dataset from the NBA games and statistics, and get back to counting rebounds in the drb field. A preliminary query informs us that we have stats ranging from 10 to 54 rebounds per team in a single game, a good information we can use in the following query:

  <span class="keyword">select</span> width_bucket(drb, <span class="number">10</span>, <span class="number">54</span>, <span class="number">9</span>) <span class="keyword">as</span> buckets,
         <span class="keyword">count</span>(*)
    <span class="keyword">from</span> team_stats
<span class="keyword">group</span> <span class="keyword">by</span> buckets
<span class="keyword">order</span> <span class="keyword">by</span> buckets;

We asked for 9 separations so we have 10 groups as a result:

 width_bucket | count 
--------------+-------
            1 |    52
            2 |  1363
            3 |  8832
            4 | 20917
            5 | 20681
            6 |  9166
            7 |  2093
            8 |   247
            9 |    20
           10 |     1
(10 rows)