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Display MySQL histogram with negative values?
For negative values, use reverse() along with concat(). Let us first create a table −
mysql> create table DemoTable632 ( histogramId int NOT NULL AUTO_INCREMENT PRIMARY KEY,histogramValue int,histogramImage text ); Query OK, 0 rows affected (0.78 sec)
Insert some records in the table using insert command −
mysql> insert into DemoTable632(histogramValue) values(2); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable632(histogramValue) values(3); Query OK, 1 row affected (0.34 sec) mysql> insert into DemoTable632(histogramValue) values(-6); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable632(histogramValue) values(-5); Query OK, 1 row affected (0.13 sec)
Display all records from the table using select statement −
mysql> select *from DemoTable632;
This will produce the following output −
+-------------+----------------+----------------+ | histogramId | histogramValue | histogramImage | +-------------+----------------+----------------+ | 1 | 2 | NULL | | 2 | 3 | NULL | | 3 | -6 | NULL | | 4 | -5 | NULL | +-------------+----------------+----------------+ 4 rows in set (0.00 sec)
Here is the query to histogram with negative values −
mysql> SELECT histogramId, histogramValue, CONCAT(
REVERSE(RPAD(REPEAT('*', IF(histogramValue<0,-histogramValue,0)), 100, ' ')),
REPEAT('*',IF(histogramValue<0,0,histogramValue))
)
AS histogramImage FROM DemoTable632 ORDER BY histogramId;This will produce the following output −
+-------------+----------------+----------------+ | histogramId | histogramValue | histogramImage | +-------------+----------------+----------------+ | 1 | 2 | ** | | 2 | 3 | *** | | 3 | -6 | ****** | | 4 | -5 | ***** | +-------------+----------------+----------------+ 4 rows in set (0.00 sec)
Updated on: 02-Jul-2020
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