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Select distinct values from three columns and display in a single column with MySQL
For this, use UNION more than once in a single MySQL query. Let us first create a table −
mysql> create table DemoTable -> ( -> Value1 int, -> Value2 int, -> Value3 int -> ); Query OK, 0 rows affected (0.69 sec)
Insert some records in the table using insert command −
mysql> insert into DemoTable values(20,null,null); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable values(20,null,null); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable values(20,null,null); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable values(10,null,null); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable values(80,20,100); Query OK, 1 row affected (0.09 sec) mysql> insert into DemoTable values(10,null,null); Query OK, 1 row affected (0.16 sec)
Display all records from the table using select statement −
mysql> select *from DemoTable;
This will produce the following output −
+--------+--------+--------+ | Value1 | Value2 | Value3 | +--------+--------+--------+ | 20 | NULL | NULL | | 20 | NULL | NULL | | 20 | NULL | NULL | | 10 | NULL | NULL | | 80 | 20 | 100 | | 10 | NULL | NULL | +--------+--------+--------+ 6 rows in set (0.00 sec)
Following is the query to select distinct values from 3 columns into 1 −
mysql> select *from -> ( -> select Value1 as AllValue from DemoTable -> union -> select Value2 as AllValue from DemoTable -> union -> select Value3 as AllValue from DemoTable -> ) tbl where AllValue IS NOT NULL -> order by AllValue;
This will produce the following output −
+----------+ | AllValue | +----------+ | 10 | | 20 | | 80 | | 100 | +----------+ 4 rows in set (0.00 sec)
Updated on: 13-Dec-2019
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