MYSQL How to query to show data in separate columns from one field

MySQL

sorry if my question is worded poorly, my SQL vocabulary is very poor.

So basically, suppose I had a table as so:

CREATE TABLE MYTABLE
{
item_id int AUTO_INCREMENT PRIMARY KEY,
item_name VARCHAR(20)
};
INSERT INTO MYTABLE (item_name) VALUES
('Fred'),
('Arthur'),
('Jane');

Now i want to fetch data that lists "Fred", "Arthur", and "Jane" into three separate columns. Is there a way to do this?

Best Answer

ORACLE, NOT MYSQL

CREATE TABLE MYTABLE ( item_id int PRIMARY KEY, item_name VARCHAR(20) ); 

INSERT INTO MYTABLE (item_id,item_name) VALUES (1,'Fred'); 

INSERT INTO MYTABLE (item_id,item_name) VALUES (2,'Arthur');

INSERT INTO MYTABLE (item_id,item_name) VALUES (3,'Jane');

select * from mytable;

**ITEM_ID ITEM_NAME**           
---------- --------------------
         1 Fred                
         2 Arthur              
         3 Jane                

3 rows selected.


select 
  item_id, 
  (select unique item_name
     from MYTABLE
     where item_name='Fred') as fred,  
  (select unique item_name
     from MYTABLE
     where item_name='Arthur') as Arthur,
  (select unique item_name
     from MYTABLE
     where item_name='Jane') as Jane
from MYTABLE;
/

   ITEM_ID FRED                 ARTHUR               JANE                
---------- -------------------- -------------------- --------------------
         1 Fred                 Arthur               Jane                
         2 Fred                 Arthur               Jane                
         3 Fred                 Arthur               Jane                

3 rows selected.

I am only learning but this works, remember subquery must return only one row, otherwise there will be error.

One more, this should work faster:

select 
 item_id,
 decode(item_name,'Fred',1,0) as Fred,
 decode(item_name,'Arthur',1,0) as arthur,
 decode(item_name,'Jane',1,0) as jane
from MYTABLE;

  ITEM_ID       FRED      ARTHUR        JANE
---------- ---------- ---------- ----------
         1          1          0          0
         2          0          1          0
         3          0          0          1

3 rows selected.

Hope this helps.

Related Solutions

Mysql – Drop auto increment hack w/o alter table

I tried something similar just now

Here is MySQL for My PC

mysql> select * from information_schema.global_variables where variable_name='datadir' or variable_name like 'versio%';
+-------------------------+------------------------------+
| VARIABLE_NAME           | VARIABLE_VALUE               |
+-------------------------+------------------------------+
| VERSION_COMMENT         | MySQL Community Server (GPL) |
| VERSION                 | 5.5.12-log                   |
| VERSION_COMPILE_MACHINE | x86                          |
| DATADIR                 | C:\MySQL_5.5.12\data\        |
| VERSION_COMPILE_OS      | Win64                        |
+-------------------------+------------------------------+
5 rows in set (0.00 sec)

I will run this using MyISAM

Step 01) create a table called 'rolando'
Step 02) insert 'dominique' and 'diamond'
Step 03) copy the table structure to 'pamela'
Step 04) alter 'pamela' to not have auto_increment
Step 05) In DOS, copy rolando.MYD to pamela.MYD
Step 06) run REPAIR TABLE pamela; (Rebuild pamela.MYI)
Step 07) run SELECT COUNT(1) FROM pamela;
Step 08) run SHOW CREATE TABLE pamela\G
Step 09) run SELECT * FROM pamela;
Step 10) insert 'carlik' into pamela
Step 11) run SELECT * FROM pamela;

Let's see if these steps are kosher.

Here are Steps 1-4

mysql> drop table if exists rolando;
Query OK, 0 rows affected (0.02 sec)

mysql> drop table if exists pamela;
Query OK, 0 rows affected (0.00 sec)

mysql> create table rolando
    -> (
    ->     name varchar(20),
    ->     id int not null auto_increment,
    ->     primary key (id)
    -> ) ENGINE=MyISAM;
Query OK, 0 rows affected (0.05 sec)

mysql> insert into rolando (name) values ('dominique'),('diamond');
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> select * from rolando;
+-----------+----+
| name      | id |
+-----------+----+
| dominique |  1 |
| diamond   |  2 |
+-----------+----+
2 rows in set (0.00 sec)

mysql> create table pamela like rolando;
Query OK, 0 rows affected (0.05 sec)

mysql> show create table rolando\G
*************************** 1. row ***************************
       Table: rolando
Create Table: CREATE TABLE `rolando` (
  `name` varchar(20) DEFAULT NULL,
  `id` int(11) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=3 DEFAULT CHARSET=latin1
1 row in set (0.00 sec)

mysql> show create table pamela\G
*************************** 1. row ***************************
       Table: pamela
Create Table: CREATE TABLE `pamela` (
  `name` varchar(20) DEFAULT NULL,
  `id` int(11) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1
1 row in set (0.02 sec)

mysql> alter table pamela modify id int(11) unsigned not null;
Query OK, 0 rows affected (0.11 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> show create table pamela\G
*************************** 1. row ***************************
       Table: pamela
Create Table: CREATE TABLE `pamela` (
  `name` varchar(20) DEFAULT NULL,
  `id` int(11) unsigned NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1
1 row in set (0.00 sec)

mysql> select count(1) from pamela;
+----------+
| count(1) |
+----------+
|        0 |
+----------+
1 row in set (0.01 sec)

mysql>

Here is Step 6

C:\>copy C:\MySQL_5.5.12\data\test\rolando.MYD C:\MySQL_5.5.12\data\test\pamela.MYD
        1 file(s) copied.

C:\>

Here are the rest of the Steps starting at Step 7

mysql> repair table pamela;
+-------------+--------+----------+------------------------------------+
| Table       | Op     | Msg_type | Msg_text                           |
+-------------+--------+----------+------------------------------------+
| test.pamela | repair | warning  | Number of rows changed from 0 to 2 |
| test.pamela | repair | status   | OK                                 |
+-------------+--------+----------+------------------------------------+
2 rows in set (0.03 sec)

mysql> select count(1) from pamela;
+----------+
| count(1) |
+----------+
|        2 |
+----------+
1 row in set (0.00 sec)

mysql> insert into pamela (name,id) values ('carlik',3);
Query OK, 1 row affected (0.00 sec)

mysql> select * from pamela;
+-----------+----+
| name      | id |
+-----------+----+
| dominique |  1 |
| diamond   |  2 |
| carlik    |  3 |
+-----------+----+
3 rows in set (0.00 sec)

mysql>

Dangerous game, isn't it ???

Guess what? Stuff like this is actually published in "High Performance MySQL : Optimization, Backups, Replication, and more", Pages 146-148 under the Subheading Speeding Up ALTER TABLE. Page 147 Paragraph 1 says:

The technique we are about to demonstrate is unsupported, undocumented, and may not work. Use it at your risk. We advise you to back up you data first!

I also had an earlier post when someone ask a similar question : Can I rename the values in a MySQL ENUM column in one query?

You got guts, @atxdba !!!

Mysql – How to join two table and show one query result in MySQL

Here is the query you need:

SELECT name FROM
(
    SELECT name FROM table1
    UNION
    SELECT name FROM table2
) A;

Here is some sample code based on your question:

use test
drop table if exists table1;
drop table if exists table2;
create table table1
(
    id int not null auto_increment,
    name varchar(10),
    primary key (id)
);
create table table2 like table1;
insert into table1 (name) values ('A'),('B'),('C');
insert into table2 (name) values ('C'),('D'),('E');
SELECT name FROM
(
    SELECT name FROM table1
    UNION
    SELECT name FROM table2
) A;

Here is the execution of that sample code:

mysql> drop table if exists table1;
Query OK, 0 rows affected (0.03 sec)

mysql> drop table if exists table2;
Query OK, 0 rows affected (0.03 sec)

mysql> create table table1 (
    ->     id int not null auto_increment,
    ->     name varchar(10),
    ->     primary key (id)
    -> );
Query OK, 0 rows affected (0.05 sec)

mysql> create table table2 like table1;
Query OK, 0 rows affected (0.06 sec)

mysql> insert into table1 (name) values ('A'),('B'),('C');
Query OK, 3 rows affected (0.06 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> insert into table2 (name) values ('C'),('D'),('E');
Query OK, 3 rows affected (0.11 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> SELECT name FROM (SELECT name FROM table1
    -> UNION SELECT name FROM table2) A;
+------+
| name |
+------+
| A    |
| B    |
| C    |
| D    |
| E    |
+------+
5 rows in set (0.00 sec)

mysql>

Give it a Try !!!

Best Answer

Related Solutions

Mysql – Drop auto increment hack w/o alter table

Mysql – How to join two table and show one query result in MySQL

Related Question