[Oracle tutorial] Use PL/SQL to draw a Histogram

Currently, an MV in the library is used to calculate the hourly traffic volume. The data is as follows:

SQL> select * from mv_time_stat;



TIME CNT

--------------------

0 187

1 51

2 34

3 19

4 19

5 20

6 50

7 107

8 682

9 1342

10 1854

11 1292

12 1416

13 1180

14 1217

15 1573

16 1785

17 1469

18 1892

19 1907

20 1602

21 1540

22 1013

23 441



24 rows selected.



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On a particular day of the year, I had a whimsy. I planned to draw a histogram based on the above data under sqlplus. First I wrote a vertical column (because it is easy to write ):


Code :--------------------------------------------------------------------------------
SQL> COL Time FORMAT A7
SQL> SELECT LPAD (DECODE (TIME, TO_CHAR (SYSDATE, 'hh24'), 'Now: '| TO_CHAR (TIME), TO_CHAR (TIME), 7 ,'') AS "Time ",
2 SUBSTR ('| LPAD ('> '| CNT, CEIL (CNT/. TOTAL * 300) + LENGTH (TO_CHAR (CNT) + 1, '-'), 1, 35) AS "Count per hour"
3 FROM MV_TIME_STAT, (select sum (CNT) as total from MV_TIME_STAT);
COL Time CLEAR

Time Count per hour
------------------------------------------------------------------------
0 | --> 187
1 |> 51
2 |> 34
3 |> 19
4 |> 19
5 |> 20
6 |> 50
7 |-> 107
NOW: 8 | ---------> 682
9 | -----------------> 1342
10 | ------------------------> 1854
11 | -----------------> 1292
12 | ------------------> 1416
13 | ---------------> 1180
14 | ----------------> 1217
15 | --------------------> 1573
16 | -----------------------> 1785
17 | -------------------> 1469
18 | -------------------------> 1892
19 | -------------------------> 1907
20 | ---------------------> 1602
21 | --------------------> 1540
22 | -------------> 1013
23 | -----> 441

24 rows selected .--------------------------------------------------------------------------------

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