I have to insert data to db in form fields that have the same path and i want to save it different id's but rather it concatenated it with ",", how could i possibly do it?
I tried to make some alias in SQL but it saves into same db field name with concatenated with ","
i expected in db when i insert that
EX.
db field name = description
input 1 value = "john";
input 2 value = "doe";
id description
1 john
2 doe
above is my expected result
but in my case when i insert it shows these
id description
1 john,doe
can someone help me to achieve that result ? THANKYOU!
Let me present a similar situation. You have a database of people and you are concerned that each person might have multiple phone numbers.
CREATE TABLE Persons (
person_id INT UNSIGNED AUTO_INCREMENT,
...
PRIMARY KEY(person_id) );
CREATE TABLE PhoneNumbers (
person_id INT UNSIGNED,
phone VARCHAR(20) CHARACTER SET ascii,
type ENUM('unknown', 'cell', 'home', 'work'),
PRIMARY KEY(person_id, phone) );
The table PhoneNumbers has a "many-to-1" relationship between phone numbers and persons. (It does not care if two persons share the same number.)
SELECT ...
GROUP CONCAT(pn.phone) AS phone_numbers,
...
FROM Persons AS p
LEFT JOIN PhoneNumbers AS pn USING(person_id)
...;
will deliver a commalist of phone numbers (eg: 123-456-7890,333-444-5555) for each person being selected. Because of the LEFT, it will deliver NULL in case a person has no associated phones.
To address your other question: It is not practical to split a commalist into the components.
Related
I am creating a viewer for PostgreSQL. My SQL needs to sort on the type that is normal for that column. Take for example:
Table:
CREATE TABLE contacts (id serial primary key, name varchar)
SQL:
SELECT id::text FROM contacts ORDER BY id;
Gives:
1
10
100
2
Ok, so I change the SQL to:
SELECT id::text FROM contacts ORDER BY id::regtype;
Which reults in:
1
2
10
100
Nice! But now I try:
SELECT name::text FROM contacts ORDER BY name::regtype;
Which results in:
invalid type name "my first string"
Google is no help. Any ideas? Thanks
Repeat: the error is not my problem. My problem is that I need to convert each column to text, but order by the normal type for that column.
regtype is a object identifier type and there is no reason to use it when you are not referring to system objects (types in this case).
You should cast the column to integer in the first query:
SELECT id::text
FROM contacts
ORDER BY id::integer;
You can use qualified column names in the order by clause. This will work with any sortable type of column.
SELECT id::text
FROM contacts
ORDER BY contacts.id;
So, I found two ways to accomplish this. The first is the solution #klin provided by querying the table and then constructing my own query based on the data. An untested psycopg2 example:
c = conn.cursor()
c.execute("SELECT * FROM contacts LIMIT 1")
select_sql = "SELECT "
for row in c.description:
if row.name == "my_sort_column":
if row.type_code == 23:
sort_by_sql = row.name + "::integer "
else:
sort_by_sql = row.name + "::text "
c.execute("SELECT * FROM contacts " + sort_by_sql)
A more elegant way would be like this:
SELECT id::text AS _id, name::text AS _name AS n FROM contacts ORDER BY id
This uses aliases so that ORDER BY still picks up the original data. The last option is more readable if nothing else.
I have a table where a user inputs name, dob, etc. and I have a User_Name column that I want automatically populated from other columns.
For example input is: Name - John Doe, DOB - 01/01/1900
I want the User_Name column to be automatically populated with johndoe01011900 (I already have the algorithm to concatenate the column parts to achieve the desired result)
I just need to know how (SQL, Trigger) to have the User_Name column filled once the user completes imputing ALL target columns. What if the user skips around and does not input the data in order? Of course the columns that are needed are (not null).
This should do it:
you can use a calculated field with the following calculation:
LOWER(REPLACE(Name, ' ', ''))+CONVERT( VARCHAR(10), DateOfBirth, 112))
In the below sample I have used a temp table but this is the same for regular tables as well.
SAMPLE:
CREATE TABLE #temp(Name VARCHAR(100)
, DateOfBirth DATE
, CalcField AS LOWER(REPLACE(Name, ' ', ''))+CONVERT( VARCHAR(10), DateOfBirth, 112));
INSERT INTO #temp(Name
, DateOfBirth)
VALUES
('John Doe'
, '01/01/1900');
SELECT *
FROM #temp;
RESULT:
I am trying to create a database for movielens (http://grouplens.org/datasets/movielens/). We've got movies and ratings. Movies have multiple genres. I splitted those out into a separate table since it's a 1:many relationship. There's a many:many relationship as well, users to movies. I need to be able to query this table multiple ways.
So I created:
CREATE TABLE genre (
genre_id serial NOT NULL,
genre_name char(20) DEFAULT NULL,
PRIMARY KEY (genre_id)
)
.
INSERT INTO genre VALUES
(1,'Action'),(2,'Adventure'),(3,'Animation'),(4,'Children\s'),(5,'Comedy'),(6,'Crime'),
(7,'Documentary'),(8,'Drama'),(9,'Fantasy'),(10,'Film-Noir'),(11,'Horror'),(12,'Musical'),
(13,'Mystery'),(14,'Romance'),(15,'Sci-Fi'),(16,'Thriller'),(17,'War'),(18,'Western');
.
CREATE TABLE movie (
movie_id int NOT NULL DEFAULT '0',
movie_name char(75) DEFAULT NULL,
movie_year smallint DEFAULT NULL,
PRIMARY KEY (movie_id)
);
.
CREATE TABLE moviegenre (
movie_id int NOT NULL DEFAULT '0',
genre_id tinyint NOT NULL DEFAULT '0',
PRIMARY KEY (movie_id, genre_id)
);
I dont know how to import my movies.csv with columns movie_id, movie_name and movie_genre For example, the first row is (1;Toy Story (1995);Animation|Children's|Comedy)
If I INSERT manually, it should be look like:
INSERT INTO moviegenre VALUES (1,3),(1,4),(1,5)
Because 3 is Animation, 4 is Children and 5 is Comedy
How can I import all data set this way?
You should first create a table that can ingest the data from the CSV file:
CREATE TABLE movies_csv (
movie_id integer,
movie_name varchar,
movie_genre varchar
);
Note that any single quotes (Children's) should be doubled (Children''s). Once the data is in this staging table you can copy the data over to the movie table, which should have the following structure:
CREATE TABLE movie (
movie_id integer, -- A primary key has implicit NOT NULL and should not have default
movie_name varchar NOT NULL, -- Movie should have a name, varchar more flexible
movie_year integer, -- Regular integer is more efficient
PRIMARY KEY (movie_id)
);
Sanitize your other tables likewise.
Now copy the data over, extracting the unadorned name and the year from the CSV name:
INSERT INTO movie (movie_id, movie_name)
SELECT parts[1], parts[2]::integer
FROM movies_csv, regexp_matches(movie_name, '([[:ascii:]]*)\s\(([\d]*)\)$') p(parts)
Here the regular expression says:
([[:ascii:]]*) - Capture all characters until the matches below
\s - Read past a space
\( - Read past an opening parenthesis
([\d]*) - Capture any digits
\) - Read past a closing parenthesis
$ - Match from the end of the string
So on input "Die Hard 17 (John lives forever) (2074)" it creates a string array with {'Die Hard 17 (John lives forever)', '2074'}. The scanning has to be from the end $, assuming all movie titles end with the year of publication in parentheses, in order to preserve parentheses and numbers in movie titles.
Now you can work on the movie genres. You have to split the string on the bar | using the regex_split_to_table() function and then join to the genre table on the genre name:
INSERT INTO moviegenre
SELECT movie_id, genre_id
FROM movies_csv, regexp_split_to_table(movie_genre, '\|') p(genre) -- escape the |
JOIN genre ON genre.genre_name = p.genre;
After all is done and dusted you can delete the movies_csv table.
I am modeling my database in Cassandra, coming from RDBMS. I want to know how can I create a one-to-many relationship which is embedded in the same Column Name and model my table to fit the following query needs.
For example:
Boxes:{
23442:{
belongs_to_user: user1,
box_title: 'the box title',
items:{
1: {
name: 'itemname1',
size: 44
},
2: {
name: 'itemname2',
size: 24
}
}
},
{ ... }
}
I read that its preferable to use composite columns instead of super columns, so I need an example of the best way to implement this. My queries are like:
Get items for box by Id
get top 20 boxes with their items (for displaying a range of boxes with their items on the page)
update items size by item id (increment size by a number)
get all boxes by userid (all boxes that belongs to a specific user)
I am expecting lots of writes to change the size of each item in the box. I want to know the best way to implement it without the need to use super columns. Furthermore, I don't mind getting a solution that takes Cassandra 1.2 new features into account, because I will use that in production.
Thanks
This particular model is somewhat challenging, for a number of reasons.
For example, with the box ID as a row key, querying for a range of boxes will require a range query in Cassandra (as opposed to a column slice), which means the use of an ordered partitioner. An ordered partitioner is almost always a Bad Idea.
Another challenge comes from the need to increment the item size, as this calls for the use of a counter column family. Counter column families store counter values only.
Setting aside the need for a range of box IDs for a moment, you could model this using multiple tables in CQL3 as follows:
CREATE TABLE boxes (
id int PRIMARY KEY,
belongs_to_user text,
box_title text,
);
CREATE INDEX useridx on boxes (belongs_to_user);
CREATE TABLE box_items (
id int,
item int,
size counter,
PRIMARY KEY(id, item)
);
CREATE TABLE box_item_names (
id int PRIMARY KEY,
item int,
name text
);
BEGIN BATCH
INSERT INTO boxes (id, belongs_to_user, box_title) VALUES (23442, 'user1', 'the box title');
INSERT INTO box_items (id, item, name) VALUES (23442, 1, 'itemname1');
INSERT INTO box_items (id, item, name) VALUES (23442, 1, 'itemname2');
UPDATE box_items SET size = size + 44 WHERE id = 23442 AND item = 1;
UPDATE box_items SET size = size + 24 WHERE id = 23442 AND item = 2;
APPLY BATCH
-- Get items for box by ID
SELECT size FROM box_items WHERE id = 23442 AND item = 1;
-- Boxes by user ID
SELECT * FROM boxes WHERE belongs_to_user = 'user1';
It's important to note that the BATCH mutation above is both atomic, and isolated.
Technically speaking, you could also denormalize all of this into a single table. For example:
CREATE TABLE boxes (
id int,
belongs_to_user text,
box_title text,
item int,
name text,
size counter,
PRIMARY KEY(id, item, belongs_to_user, box_title, name)
);
UPDATE boxes set size = item_size + 44 WHERE id = 23442 AND belongs_to_user = 'user1'
AND box_title = 'the box title' AND name = 'itemname1' AND item = 1;
SELECT item, name, size FROM boxes WHERE id = 23442;
However, this provides no guarantees of correctness. For example, this model makes it possible for items of the same box to have different users, or titles. And, since this makes boxes a counter column family, it limits how you can evolve the schema in the future.
I think in PlayOrm's objects first, then show the column model below....
Box {
#NoSqlId
String id;
#NoSqlEmbedded
List<Item> items;
}
User {
#NoSqlId
TimeUUID uuid;
#OneToMany
List<Box> boxes;
}
The User then is a row like so
rowkey = uuid=<someuuid> boxes.fkToBox35 = null, boxes.fktoBox37=null, boxes.fkToBox38=null
Note, the form of the above is columname=value where some of the columnnames are composite and some are not.
The box is more interesting and say Item has fields name and idnumber, then box row would be
rowkey = id=myid, items.item23.name=playdo, items.item23.idnumber=5634, itesm.item56.name=pencil, items.item56.idnumber=7894
I am not sure what you meant though on get the top 20 boxes? top boxes meaning by the number of items in them?
Dean
You can use Query-Driven Methodology, for data modeling.You have the three broad access paths:
1) partition per query
2) partition+ per query (one or more partitions)
3) table or table+ per query
The most efficient option is the “partition per query”. This article can help you in this case, step-by-step. it's sample is exactly a one-to-many relation.
And according to this, you will have several tables with some similar columns. You can manage this, by Materialized View or batch-log(as alternative approach).
We want to use cassandra to store complex data
but we can't figure out how to organize indexes.
Our table (column family) looks like this:
Users =
{
RandomId int,
Firstname varchar,
Lastname varchar,
Age int,
Country int,
ChildCount int
}
We have queries with mandatory fields (Firstname, Lastname, Age) and extra search options (Country, ChildCount).
How should we organize the index to make this kind of queries faster?
First I thought, it would be natural to make composite index on (Firstname, Lastname, Age) and add separate secondary index on remaining fields (Country and ChildCount).
But I can't insert rows into table after creating secondary indexes and I can't query the table.
Using
cassandra 1.1.0
cqlsh with --cql3 option.
Any other suggestions to solve our problem (complex queries with mandatory and additional options) are welcome.
This is my idea. You could simply create a column family with your RandomId as the row key and all the remaining fields simply as columns (e.g. column name 'firstname', column value 'jonh'). After this you have to create a secondary index for each of these columns. The cardinality of your values seems to be low so it should be slightly efficient.
THe CQL code should be something like:
create column family users with comparator=UTF8Type and column_metadata=[{column_name: firstname, validation_class: UTF8Type,index_type: KEYS},
{column_name: lastname, validation_class: UTF8Type, index_type: KEYS},
{column_name: contry, validation_class: IntegerType, index_type: KEYS},
{column_name: age, validation_class: IntegerType, index_type: KEYS]},
{column_name: ChildCount, validation_class: IntegerType, index_type: KEYS]];
A good reference for it could be http://www.datastax.com/docs/0.7/data_model/secondary_indexes
Let me know if I'm wrong;
For queries involving a large number of partitions indices are not very efficient.
I think it is better to think the tables based on the queries you'd want to make: you want a table for queries based on user name and that seems like the right place to store all the info concerning the user. On the other hand you want to be able to search based on country, I assumed, to provide a list of users: for that you don't really need all the info, maybe just the first and last names, or just the email, etc. Another table could do it then.
This involves some data duplication but that better fits the Cassandra data modelling ideas.
This would give:
CREATE TABLE users(
id UUID,
lastname TEXT,
firstname TEXT,
age INT,
country TEXT,
childcount INT,
PRIMARY KEY(UUID)
);
CREATE TABLE users_by_country(
country TEXT,
firstname TEXT,
lastname TEXT,
user_uuid UUID,
PRIMARY KEY((country), firstname, lastname)
);
CREATE TABLE users_by_age(
age INT,
firstname TEXT,
lastname TEXT,
user_uuid UUID,
PRIMARY KEY((age), firstname, lastname)
);