Very short answer : No new datatypes have been created to accommodate you.
While we are on this subject
Let's try plain SQL
USE test
DROP TABLE IF EXISTS numtest;
CREATE TABLE numtest
(
id int not null auto_increment,
xx decimal(10,3) default null,
primary key (id)
);
INSERT INTO numtest (id) values (0),(0),(0),(0),(0);
SELECT * FROM numtest;
Does this work ???
mysql> USE test
Database changed
mysql> DROP TABLE IF EXISTS numtest;
Query OK, 0 rows affected (0.01 sec)
mysql> CREATE TABLE numtest
-> (
-> id int not null auto_increment,
-> xx decimal(10,3) default null,
-> primary key (id)
-> );
Query OK, 0 rows affected (0.03 sec)
mysql> INSERT INTO numtest (id) values (0),(0),(0),(0),(0);
Query OK, 5 rows affected (0.00 sec)
Records: 5 Duplicates: 0 Warnings: 0
mysql> SELECT * FROM numtest;
+----+------+
| id | xx |
+----+------+
| 1 | NULL |
| 2 | NULL |
| 3 | NULL |
| 4 | NULL |
| 5 | NULL |
+----+------+
5 rows in set (0.00 sec)
mysql>
OK, fine. It works with SQL. You are asking about LOAD DATA INFILE
You brought up a post I answered : MySQL is inserting "" as 0 in decimal fields. How to stop that?
Let's see if that bug was addressed since it was submitted. I will try to duplicate the code in that bug that did not work.
First let's create that table from the bug report
mysql> USE test
Database changed
mysql> DROP TABLE IF EXISTS bug_repeat;
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> CREATE TABLE bug_repeat
-> (
-> name varchar(10),
-> price decimal(12,6)
-> )
-> ENGINE=MYISAM DEFAULT CHARSET=ascii COLLATE=ascii_bin;
Query OK, 0 rows affected (0.00 sec)
mysql> SHOW CREATE TABLE bug_repeat\G
*************************** 1. row ***************************
Table: bug_repeat
Create Table: CREATE TABLE `bug_repeat` (
`name` varchar(10) COLLATE ascii_bin DEFAULT NULL,
`price` decimal(12,6) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=ascii COLLATE=ascii_bin
1 row in set (0.00 sec)
mysql>
Next, let's make some data
C:\>type C:\MySQLDBA\bug_test.txt
name,
name,0
,
name,6
name,2
name,
name,0
name,0
name,
name,0
C:\>
Let's run the LOAD DATA INFILE
mysql> load data local infile 'C:/MySQLDBA/bug_test.txt'
-> into table test.bug_repeat
-> fields terminated by ','
-> lines terminated by '\n';
Query OK, 10 rows affected, 4 warnings (0.00 sec)
Records: 10 Deleted: 0 Skipped: 0 Warnings: 4
Ouch, what happened
mysql> show warnings\G
*************************** 1. row ***************************
Level: Warning
Code: 1366
' for column 'price' at row 1lue: '
*************************** 2. row ***************************
Level: Warning
Code: 1366
' for column 'price' at row 3lue: '
*************************** 3. row ***************************
Level: Warning
Code: 1366
' for column 'price' at row 6lue: '
*************************** 4. row ***************************
Level: Warning
Code: 1366
' for column 'price' at row 9lue: '
4 rows in set (0.00 sec)
mysql> select * from bug_repeat;
+------+----------+
| name | price |
+------+----------+
| name | 0.000000 |
| name | 0.000000 |
| | 0.000000 |
| name | 6.000000 |
| name | 2.000000 |
| name | 0.000000 |
| name | 0.000000 |
| name | 0.000000 |
| name | 0.000000 |
| name | 0.000000 |
+------+----------+
10 rows in set (0.00 sec)
mysql>
What's the sql_mode ?
mysql> select @@sql_mode;
+------------------------+
| @@sql_mode |
+------------------------+
| NO_ENGINE_SUBSTITUTION |
+------------------------+
1 row in set (0.00 sec)
mysql>
Let's blank out the sql_mode, truncate the table and reload
mysql> set sql_mode = '';
Query OK, 0 rows affected (0.00 sec)
mysql> select @@sql_mode;
+------------+
| @@sql_mode |
+------------+
| |
+------------+
1 row in set (0.00 sec)
mysql> truncate table bug_repeat;
Query OK, 0 rows affected (0.00 sec)
mysql> load data local infile 'C:/MySQLDBA/bug_test.txt'
-> into table test.bug_repeat
-> fields terminated by ','
-> lines terminated by '\n';
Query OK, 10 rows affected, 4 warnings (0.02 sec)
Records: 10 Deleted: 0 Skipped: 0 Warnings: 4
mysql> show warnings\G
*************************** 1. row ***************************
Level: Warning
Code: 1366
' for column 'price' at row 1lue: '
*************************** 2. row ***************************
Level: Warning
Code: 1366
' for column 'price' at row 3lue: '
*************************** 3. row ***************************
Level: Warning
Code: 1366
' for column 'price' at row 6lue: '
*************************** 4. row ***************************
Level: Warning
Code: 1366
' for column 'price' at row 9lue: '
4 rows in set (0.00 sec)
mysql>
Let doctor the input file with \N
like the bug report had
C:\>type C:\MySQLDBA\bug_test.txt
name,\N
name,0
\N,\N
name,6
name,2
name,\N
name,0
name,0
name,\N
name,0
C:\>
Let's repeat all of this with InnoDB
mysql> USE test
Database changed
mysql> DROP TABLE IF EXISTS bug_repeat;
Query OK, 0 rows affected (0.00 sec)
mysql> CREATE TABLE bug_repeat
-> (
-> name varchar(10),
-> price decimal(12,6)
-> )
-> ENGINE=InnoDB;
Query OK, 0 rows affected (0.05 sec)
mysql> truncate table bug_repeat;
Query OK, 0 rows affected (0.05 sec)
mysql> load data local infile 'C:/MySQLDBA/bug_test.txt'
-> into table test.bug_repeat
-> fields terminated by ','
-> lines terminated by '\n';
Query OK, 10 rows affected, 4 warnings (0.00 sec)
Records: 10 Deleted: 0 Skipped: 0 Warnings: 4
mysql> show warnings\G
*************************** 1. row ***************************
Level: Warning
Code: 1366
' for column 'price' at row 1lue: 'N
*************************** 2. row ***************************
Level: Warning
Code: 1366
' for column 'price' at row 3lue: 'N
*************************** 3. row ***************************
Level: Warning
Code: 1366
' for column 'price' at row 6lue: 'N
*************************** 4. row ***************************
Level: Warning
Code: 1366
' for column 'price' at row 9lue: 'N
4 rows in set (0.00 sec)
mysql> select * from bug_repeat;
+------+----------+
| name | price |
+------+----------+
| name | 0.000000 |
| name | 0.000000 |
| NULL | 0.000000 |
| name | 6.000000 |
| name | 2.000000 |
| name | 0.000000 |
| name | 0.000000 |
| name | 0.000000 |
| name | 0.000000 |
| name | 0.000000 |
+------+----------+
10 rows in set (0.00 sec)
mysql>
What version of MySQL am I using ???
mysql> show global variables like 'version%';
+-------------------------+------------------------------+
| Variable_name | Value |
+-------------------------+------------------------------+
| version | 5.6.22 |
| version_comment | MySQL Community Server (GPL) |
| version_compile_machine | x86_64 |
| version_compile_os | Win64 |
+-------------------------+------------------------------+
4 rows in set (0.00 sec)
mysql>
What about Linux ???
$ cat /tmp/bug_test.txt
name,\N
name,0
\N,\N
name,6
name,2
name,\N
name,0
name,0
name,\N
name,0
$
Logging in to mysql and trying ...
mysql> create database test;
Query OK, 1 row affected (0.01 sec)
mysql> USE test
Database changed
mysql> DROP TABLE IF EXISTS bug_repeat;
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> CREATE TABLE bug_repeat
-> (
-> name varchar(10),
-> price decimal(12,6)
-> )
-> ENGINE=InnoDB;
Query OK, 0 rows affected (0.09 sec)
mysql> truncate table bug_repeat;
Query OK, 0 rows affected (0.04 sec)
mysql> load data local infile 'C:/MySQLDBA/bug_test.txt'
-> into table test.bug_repeat
-> fields terminated by ','
-> lines terminated by '\n';
ERROR 2 (HY000): File 'C:/MySQLDBA/bug_test.txt' not found (Errcode: 2 - No such file or directory)
mysql> show warnings\G
Empty set (0.00 sec)
mysql> select * from bug_repeat;
Empty set (0.00 sec)
mysql> truncate table bug_repeat;
Query OK, 0 rows affected (0.04 sec)
mysql> load data local infile '/tmp/bug_test.txt'
-> into table test.bug_repeat
-> fields terminated by ','
-> lines terminated by '\n';
Query OK, 10 rows affected (0.00 sec)
Records: 10 Deleted: 0 Skipped: 0 Warnings: 0
mysql> show warnings\G
Empty set (0.00 sec)
mysql> select * from bug_repeat;
+------+----------+
| name | price |
+------+----------+
| name | NULL |
| name | 0.000000 |
| NULL | NULL |
| name | 6.000000 |
| name | 2.000000 |
| name | NULL |
| name | 0.000000 |
| name | 0.000000 |
| name | NULL |
| name | 0.000000 |
+------+----------+
10 rows in set (0.00 sec)
mysql> show global variables like 'version%';
+-------------------------+------------------------------+
| Variable_name | Value |
+-------------------------+------------------------------+
| version | 5.6.21-log |
| version_comment | MySQL Community Server (GPL) |
| version_compile_machine | x86_64 |
| version_compile_os | Linux |
+-------------------------+------------------------------+
4 rows in set (0.00 sec)
mysql>
Today's date ???
mysql> select now();
+---------------------+
| now() |
+---------------------+
| 2015-06-25 18:48:10 |
+---------------------+
1 row in set (0.01 sec)
mysql>
It's been a year and one week since that bug report was submitted and nothing has changed.
My answer to MySQL is inserting "" as 0 in decimal fields. How to stop that? still stands as of today.
You need to do this test against MySQL 5.6.23 and see if something has changed.
Best Answer
Without window functions this is pretty hard in MySQL. Since the two columns -
t1
andt2
- store similar content and you only want disctinct values from both, it would be much easier to get the values in a single column:I don't see any reason to have the original convoluted result, except if you want to keep info from other columns in the table and just remove duplicates from these 2 columns. And in that case, an
UPDATE
would make more sense.Here is a method to get this result, anyway. It assumes that
(id)
has aUNIQUE
constraint. Tested at dbfiddle.uk:Notice that in MariaDB (MySQL's first cousin), that has CTEs, the same query can be rewritten more compactly and more clearly:
Logically, both variations work the same way, though. This subselect:
returns all distinct
t1
andt2
values along with the ID of the first1 row where each is encountered. For your example, it produces this output:The above set is joined against the original table twice, on
t1
and ont2
. In each case, where the original row's ID matches the subselect row's ID, the value is returned intact, because the match indicates that the row is the value's first occurrence; otherwise the value is replaced with a null.1“First" in the order of ID.