Setting column values as column names in the MySQL query result?
To set column values as column names in the query result, you need to use a CASE statement.
The syntax is as follows −
select yourIdColumnName,
max(case when (yourColumnName1='yourValue1') then yourColumnName2 else NULL
end) as 'yourValue1',
max(case when (yourColumnName1='yourValue2') then yourColumnName2 else NULL
end) as 'yourValue2',
max(case when yourColumnName1='yourValue3') then yourColumnName2 else NULL
end) as 'yourValue3’,
.
.
N
from valueAsColumn
group by yourIdColumnName
order by yourIdColumnName;
To understand the above syntax, let us create a table. The query to create a table is as follows −
mysql> create table valueAsColumn
-> (
-> UserId int,
-> UserColumn1 varchar(10),
-> UserColumn2 varchar(10)
-> );
Query OK, 0 rows affected (0.75 sec)
Now you can insert some records in the table using insert command. The query is as follows −
mysql> insert into valueAsColumn values(0,'John','A+');
Query OK, 1 row affected (0.18 sec)
mysql> insert into valueAsColumn values(0,'Carol','B');
Query OK, 1 row affected (0.17 sec)
mysql> insert into valueAsColumn values(0,'Sam','C');
Query OK, 1 row affected (0.17 sec)
mysql> insert into valueAsColumn values(1,'John','D');
Query OK, 1 row affected (0.20 sec)
mysql> insert into valueAsColumn values(1,'Carol','A');
Query OK, 1 row affected (0.20 sec)
mysql> insert into valueAsColumn values(1,'Carol','C');
Query OK, 1 row affected (0.15 sec)
Display all records from the table using a select statement. The query is as follows −
mysql> select *from valueAsColumn;
The following is the output −
+--------+-------------+-------------+
| UserId | UserColumn1 | UserColumn2 |
+--------+-------------+-------------+
| 0 | John | A+ |
| 0 | Carol | B |
| 0 | Sam | C |
| 1 | John | D |
| 1 | Carol | A |
| 1 | Carol | C |
+--------+-------------+-------------+
6 rows in set (0.00 sec)
Here is the query to set column value as column names −
mysql> select UserId,
-> max(case when (UserColumn1='John') then UserColumn2 else NULL end) as 'John',
-> max(case when (UserColumn1='Carol') then UserColumn2 else NULL end) as 'Carol',
-> max(case when (UserColumn1='Sam') then UserColumn2 else NULL end) as 'Sam'
-> from valueAsColumn
-> group by UserId
-> order by UserId;
The following is the output −
+--------+------+-------+------+
| UserId | John | Carol | Sam |
+--------+------+-------+------+
| 0 | A+ | B | C |
| 1 | D | C | NULL |
+--------+------+-------+------+
2 rows in set (0.00 sec)
Published on 27-Feb-2019 14:39:58
