Select one distinct column, others can be non distinct. - MySQL
https://stackoverflow.com/questions/4613999
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26-09-2019 - |
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Ok I have a temporary table with 135000 rows, I'm trying to insert some of the values from this temporary table into other tables.
This is the schema I'm using
tvtemptable
+-------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------+-------------+------+-----+---------+-------+
| PROGTITLE | text | YES | | NULL | |
| SUBTITLE | text | YES | | NULL | |
| EPISODE | text | YES | | NULL | |
| YR | year(4) | YES | | NULL | |
| DIRECTOR | text | YES | | NULL | |
| PERFORMERS | text | YES | | NULL | |
| PREMIERE | tinyint(1) | YES | | NULL | |
| FILM | tinyint(1) | YES | | NULL | |
| RPEAT | tinyint(1) | YES | | NULL | |
| SUBTITLES | tinyint(1) | YES | | NULL | |
| WIDESCREEN | tinyint(1) | YES | | NULL | |
| NEWSERIES | tinyint(1) | YES | | NULL | |
| DEAFSIGNED | tinyint(1) | YES | | NULL | |
| BNW | tinyint(1) | YES | | NULL | |
| STARRATING | tinyint(4) | YES | | NULL | |
| CERTIFICATE | varchar(5) | YES | | NULL | |
| GENRE | varchar(50) | YES | | NULL | |
| DESCRIPTION | text | YES | | NULL | |
| CHOICE | tinyint(1) | YES | | NULL | |
| PROGDATE | date | YES | | NULL | |
| STARTIME | time | YES | | NULL | |
| ENDTIME | time | YES | | NULL | |
| DURATION | int(11) | YES | | NULL | |
| CHANNELID | int(11) | NO | | NULL | |
+-------------+-------------+------+-----+---------+-------+
channels
+-------------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+-------------+------+-----+---------+----------------+
| CHANNELID | int(11) | NO | PRI | NULL | auto_increment |
| CHANNELNAME | varchar(50) | YES | | NULL | |
+-------------+-------------+------+-----+---------+----------------+
genre
+-----------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+-------------+------+-----+---------+----------------+
| GENREID | int(11) | NO | PRI | NULL | auto_increment |
| GENRENAME | varchar(50) | YES | | NULL | |
+-----------+-------------+------+-----+---------+----------------+
programme
+-------------+------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+------------+------+-----+---------+----------------+
| PROGRAMMEID | int(11) | NO | PRI | NULL | auto_increment |
| GENREID | int(11) | NO | MUL | NULL | |
| PROGTITLE | text | YES | | NULL | |
| YR | year(4) | YES | | NULL | |
| DIRECTOR | text | YES | | NULL | |
| PERFORMERS | text | YES | | NULL | |
| FILM | tinyint(1) | YES | | NULL | |
| WIDESCREEN | tinyint(1) | YES | | NULL | |
| BNW | tinyint(1) | YES | | NULL | |
| CERTIFICATE | varchar(5) | YES | | NULL | |
| DESCRIPTION | text | YES | | NULL | |
+-------------+------------+------+-----+---------+----------------+
episode
+-------------+---------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+---------+------+-----+---------+----------------+
| EPISODEID | int(11) | NO | PRI | NULL | auto_increment |
| PROGRAMMEID | int(11) | NO | MUL | NULL | |
| SUBTITLE | text | YES | | NULL | |
| EPISODE | text | YES | | NULL | |
| DIRECTOR | text | YES | | NULL | |
| PERFORMERS | text | YES | | NULL | |
| DESCRIPTION | text | YES | | NULL | |
+-------------+---------+------+-----+---------+----------------+
channelprogramme
+--------------------+------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------------+------------+------+-----+---------+----------------+
| CHANNELPROGRAMMEID | int(11) | NO | PRI | NULL | auto_increment |
| CHANNELID | int(11) | NO | MUL | NULL | |
| PROGRAMMEID | int(11) | NO | MUL | NULL | |
| EPISODEID | int(11) | NO | MUL | NULL | |
| RPEAT | tinyint(1) | YES | | NULL | |
| NEWSERIES | tinyint(1) | YES | | NULL | |
| PREMIERE | tinyint(1) | YES | | NULL | |
| CHOICE | tinyint(1) | YES | | NULL | |
| SUBTITLES | tinyint(1) | YES | | NULL | |
| DEAFSIGNED | tinyint(1) | YES | | NULL | |
| STARRATING | tinyint(4) | YES | | NULL | |
| PROGDATE | date | YES | | NULL | |
| STARTTIME | time | YES | | NULL | |
| ENDTIME | time | YES | | NULL | |
| DURATION | tinyint(4) | YES | | NULL | |
+--------------------+------------+------+-----+---------+----------------+
So a little bit of background, the database is a TV listings database, the channelprogramme table contains all the entries for every show on every channel, the programme table contains unique entries for every program, episode contains unique entries for every episode of programs that have episodes
I think my confusion is I want to select the distinct progtitles from the temporary table to populate the programme table, but I want some other information to go with it.
For example if I did
select distinct(progtitle) from tvtemptable;
It would only return me the value for the progtitle column, whereas what I actually want is the progtitle plus some other stuff.
So if I try to select more information like so
mysql> select distinct progtitle, yr, director, film from tvtemptable
limit 30;
+-----------------------------------+------+---------------------+------+
| progtitle | yr | director | film |
+-----------------------------------+------+---------------------+------+
| Teleshopping | 2000 | | 0 |
| Cinemania | 2000 | | 0 |
| Whose Line Is It Anyway? | 2000 | | 0 |
| Just Desserts | 2004 | Kevin Connor | 1 |
| Law & Order | 2000 | Matthew Penn | 0 |
| Jane Doe: Yes, I Remember it Well | 2006 | Armand Mastroianni | 0 |
| CSI: NY | 2000 | David Jackson | 0 |
| CSI: Crime Scene Investigation | 2000 | Kenneth Fink | 0 |
| NCIS | 2000 | Colin Bucksey | 0 |
| CSI: Miami | 2000 | | 0 |
| Enter the Dragon | 1973 | Robert Clouse | 1 |
| Close | 2000 | | 0 |
| My Son Is Innocent | 1996 | Larry Elikann | 1 |
| Law & Order | 2000 | Christopher Misiano | 0 |
| Murder 101 | 2006 | Christian I Nyby II | 1 |
| CSI: NY | 2000 | Christine Moore | 0 |
| CSI: Crime Scene Investigation | 2000 | Bill Eagles | 0 |
| Rush Hour | 1998 | Brett Ratner | 1 |
| Dark Blue | 2000 | Jeffrey Hunt | 0 |
| CSI: Crime Scene Investigation | 2000 | Richard J Lewis | 0 |
| Ordinary Miracles | 2005 | Michael Switzer | 1 |
| Law & Order | 2000 | Jace Alexander | 0 |
| Wounded Heart | 1995 | Vic Sarin | 1 |
| CSI: NY | 2000 | Jonathan Glassner | 0 |
| Dark Blue | 2000 | Nathan Hope | 0 |
| Blade: The Series | 2000 | Michael Robison | 0 |
| K-Ville | 2000 | Kevin Dowling | 0 |
| Law & Order | 2000 | Jim Ellis | 0 |
| Reasons of the Heart | 1996 | Rick Jacobson | 1 |
| CSI: NY | 2000 | Anthony Hemingway | 0 |
+-----------------------------------+------+---------------------+------+
There will be a few duplicates in the progtitle column. The programmes aren't repeated for each new director, there are different directors above for some of the programmes because those programmes have episodes.
Now I've managed to get the select to work properly If I only need one extra column for example
select distinct
t1.progtitle,
(select
t2.director
from
tvtemptable t2
where
t1.progtitle = t2.progtitle
limit 1) as "Director"
from
tvtemptable t1 limit 10;
+-----------------------------------+--------------------+
| progtitle | Director |
+-----------------------------------+--------------------+
| Teleshopping | |
| Cinemania | |
| Whose Line Is It Anyway? | |
| Just Desserts | Kevin Connor |
| Law & Order | Matthew Penn |
| Jane Doe: Yes, I Remember it Well | Armand Mastroianni |
| CSI: NY | David Jackson |
| CSI: Crime Scene Investigation | Kenneth Fink |
| NCIS | Colin Bucksey |
| CSI: Miami | |
+-----------------------------------+--------------------+
Obviously this will get messy If I want to select more than one additional column
So what's the best way to do this?
This is my insert command for populating the programme table from the temporary table, currently it has the same issue with duplicates in the select example I gave above.
INSERT INTO PROGRAMME (
PROGTITLE, GENREID, YR, DIRECTOR,
PERFORMERS, FILM, WIDESCREEN, BNW,
CERTIFICATE, DESCRIPTION)
SELECT DISTINCT
T.PROGTITLE, G.GENREID, T.YR, T.DIRECTOR,
T.PERFORMERS, T.FILM, T.WIDESCREEN, T.BNW,
T.CERTIFICATE, T.DESCRIPTION
FROM
TVTEMPTABLE T
INNER JOIN GENRE G ON G.GENRENAME=T.GENRE
LEFT JOIN PROGRAMME P ON P.PROGTITLE=T.PROGTITLE
WHERE
P.PROGTITLE IS NULL
Solution
Am I right to assume that your TVTEMPTABLE is the result of a join of tables from someplace?
If that is the case, I think you will have an easier job overall, if you first split that temp table into multiple temp tables that have the same format as your target tables.
For example (and I don't know your data so I just guess):
-- All genres (matches your existing genres table)
create table genres_temp as
select distinct genre
from tvtemptable;
-- All programmes (matches your existing programme table)
create table programmes_temp as
select distinct all_the_programme_columns
from tvtemptable;
-- Contains the many-to-many relationship between genres and programmes
create table programme_genre_temp as
select distinct genre, progtitle
from tvtemptable;
The above doesn't answer your question, but it may give you some ideas that takes away the problem, which seems to be that programme information is repeated for each something. You need to find out what it is.
Updated So each programme is repeated once for each director? Then my above approach makes even more sense: Extract the entities, and relationships first.
Updated 2
Hmm, you force-fit director into programme, when director is related to the episode? That would be a modelling error it seems. Anyway, if you don't care which director you pick, you can group on progtitle and use MAX() around all other columns. That will give you distinct progtitles and one of the values for the rest of the columns.
SELECT T.PROGTITLE, max(G.GENREID), max(T.YR), max(T.DIRECTOR), etc
FROM TVTEMPTABLE T
INNER JOIN GENRE G ON G.GENRENAME=T.GENRE
LEFT JOIN PROGRAMME P ON P.PROGTITLE=T.PROGTITLE
WHERE P.PROGTITLE IS NULL
group by T.PROGTITLE;
OTHER TIPS
That doesn't make sense. How can a row be partially distinct and partially non-distinct? Think of the selected result as a table - how would you represent the data, if there is one value for PROGTITLE that has multiple values for the rest of the columns?
This doesn't answer your question, but probably will answer those for people googling their way here:
In Postgresql, you can do this with SELECT DISTINCT ON, eg:
SELECT DISTINCT ON (p.progtitle) p.* FROM progtitle p;
I don't know of any equivalent for MySQL.
Insert into xx (a,b)
Select a.ab, b.bb from (
Select distinct ab from a) a, (select distinct bb from b) b
I'm reading that what you want is a list of distinct programmes, but with some associated data in other columns for context? You can do this with row numbers.
select * from
(select *,
row_number() over (partition by progtitle order by year desc) N
from tvtempta) t
where t.N = 1
Better still, you can use the order by clause to specify the most recent, first, or some other preferred way of choosing which row you want. This is the T-SQL syntax and I think the same syntax should work in Oracle (if not it's definitely possible in Oracle). Unfortunately I don't know if you can do this in MySQL.
