I watched a few youtube videos about how to structure a database using tables and fields. I am a bit confused about how to strucuture my information.
I have put my attempt below:
// Identifier Table
// This is where we give each item a new unique identifier
UniqueID []
// Item Table
// This is where the main content goes which is displayed
UniqueID []
Title []
Description []
Date []
Location []
Coordinates []
Source []
Link []
// Misc Table
// This is additional useful information, but not displayed
geocoded []
country name []
By separating out the uniqueID when I delete a record I can make sure that new records still have a unique incrementing ID. Can I get some feedback on how I divided up my data into three tables.
you gave us no hint what you want to represent in your db.
For example: if location and coordinate describe a building or maybe room, than it could be useful to save that information in an extra table and have a relationship from item to it, as this would allow to easily fetch all items connected with on place.
Of course you should apply the same principle for country: a locations lays with-in a country.
BEGIN;
CREATE TABLE "country" (
"id" integer NOT NULL PRIMARY KEY,
"name" varchar(255) NOT NULL
)
;
CREATE TABLE "location" (
"id" integer NOT NULL PRIMARY KEY,
"name" varchar(255) NOT NULL,
"coordinate" varchar(255) NOT NULL,
"country_id" integer NOT NULL REFERENCES "country" ("id")
)
;
CREATE TABLE "item" (
"id" integer NOT NULL PRIMARY KEY,
"title" varchar(25) NOT NULL,
"description" text NOT NULL,
"date" datetime NOT NULL,
"source" varchar(255) NOT NULL,
"link" varchar(255) NOT NULL,
"location_id" integer NOT NULL REFERENCES "location" ("id")
)
;
In the case stated above I would pack everything into one table since there is not enugh complexity to benfit from spliting the data into diferent tables.
When you have more metadata you can split it up into:
Item (For display data)
ItemMeta (For meta data)
Related
I'm trying to modify the name a column named "photo_url". I tried to simply changing the string name to "test" and killing the postgresql service and then re starting it again, but it doesn't seem to be working; it still loads up as "photo_url".
I'm not sure how to change the name if anyone could help me it would be greatly appreciated.
this is my table im using postgreSQL, and pgweb to view my database, i used dbdesigner to generate this schema
CREATE TABLE "users" (
"user_id" serial NOT NULL,
"name" TEXT NOT NULL,
"instrument" TEXT NOT NULL,
"country" TEXT NOT NULL,
"state" TEXT NOT NULL,
"city" TEXT NOT NULL,
"about" TEXT NOT NULL,
"email" TEXT NOT NULL UNIQUE,
"hashed_password" TEXT NOT NULL,
"photo_url" TEXT NOT NULL,
"created_at" timestamptz NOT NULL default now(),
CONSTRAINT "users_pk" PRIMARY KEY ("user_id")
) WITH (
OIDS=FALSE
);
If you've already created the table, you can use this query to rename the column
ALTER TABLE users RENAME COLUMN photo_url TO test;
otherwise simply recreate your table with the new column name.
More information on the ALTER TABLE command can be found in the PostgreSQL Docs.
After creating the table with a unique ID autoincrement, I realize my table lack a row. But I don't know how to do this without compromising the order of other rows in the table!
TABLE flights
id INTEGER PRIMARY KEY AUTOINCREMENT,
origin TEXT NOT NULL,
destination TEXT NOT NULL,
duration INTEGER NOT NULL
I want to insert a row: 2|Shanghai|Paris|760 into the table with id = 2.
1|New York|London|415
2|Istanbul|Tokyo|700
3|New York|Paris|435
4|Moscow|Paris|245
5|Lima|New York|455
Table I wished:
1|New York|London|415
2|Shanghai|Paris|760
3|Istanbul|Tokyo|700
4|New York|Paris|435
5|Moscow|Paris|245
6|Lima|New York|455
Thanks for any advice to me!
No way you can do this with auto-increment ID because IDS are not to order rows, but to identify the rows and assert it's the only row with that ID. If you want to, use a new specific column for this purpose, this way the IDs still the same and you can sort using anything as indexes.
CREATE TABLE flights (
id INTEGER AUTO_INCREMENT,
index INTEGER NOT NULL,
origin TEXT NOT NULL,
destination TEXT NOT NULL,
duration INTEGER NOT NULL,
PRIMARY KEY (id),
UNIQUE KEY unique_index (index)
);
Here the code is written in Go. I am using two tables where one table has a foreign key that refers to the other table's primary key. Let's say I have a database as following struct defined:
type User struct{
ID uint `gorm:"primary_key;column:id"`
Name string `gorm:"column:name"`
Place place
PlaceID
}
type Place struct{
ID uint `gorm:"primary_key;column:id"`
Name string `gorm:"column:name"`
Pincode uint `gorm:"column:pincode"`
}
And the sql schema is:
create table place(
id int(20) NOT NULL AUTO_INCREMENT,
name varchar(100) NOT NULL,
pincode uint(20) NOT NULL,
PRIMARY KEY (id),
)
create table user(
id int(20) NOT NULL AUTO_INCREMENT,
name varchar(100) NOT NULL,
place_id uint(20) NOT NULL,
PRIMARY KEY (id),
FOREIGN KEY (place_id) REFERENCES place(id)
)
Now while inserting in user by gorm as:
place := Place{Name:"new delhi",Pincode:1234}
user := User{Name: "sam", Age: 15, Place: place}
err = db.Debug().Create(&user).Error
//It inserts to both user and place table in mysql
//now while updating to name in user table as Samuel and place as
//following
place := Place{Name:"mumbai",Pincode:1234}
err = db.Debug().Model(&User{}).Where("id =?",
1,).Update(&user{Name:"Samuel",Place:place}).Error
It updates the row in user table but creates a new row in place table.But it should update the matching row in place table and not create a new one
Is there any way to do it? Here I am not using auto migrate function to create db tables.
The answer to your question should be sought in a relations or Association Mode.
The example below shows how to add new associations for many to many, has many, replace current associations for has one, belongs to
db.Model(&user).Association("Place").Append(Place{Name:"mumbai",Pincode:1234})
Or you can replace current associations with new ones:
db.Model(&user).Association("Place").Replace(Place{Name:"mumbai",Pincode:1234},Place{Name:"new delhi",Pincode:1234})
Probably It's creating a new row because you didn't set the ID on Place{Name:"mumbai",Pincode:1234}.
Suppose I have this piece of data (in reality roughly 5,000 entries every few seconds, initially 50,000 from a data dump):
[
"person": {
"name": "Johnny Bravo",
"location": {
"zipcode": 11111,
"address": "1 Second Ave"
},
"phone_numbers": [ 15007774321, 12227435432 ]
}
]
and this schema:
CREATE TABLE person(
id serial PRIMARY KEY,
name varchar(255) UNIQUE,
location_id integer NOT NULL REFERENCES location(id)
)
CREATE TABLE location(
id serial PRIMARY KEY,
zipcode integer NOT NULL,
address varchar(255) NOT NULL
)
CREATE TABLE phone_number(
id serial PRIMARY KEY,
"number" integer NOT NULL
)
CREATE TABLE person_number_relationship(
id serial PRIMARY KEY,
phone_number_id integer NOT NULL REFERENCES phone_number(id),
person_id integer NOT NULL REFERENCES person(id)
)
This is an oversimplification but the parts that matter are here. Currently to insert this data I use the language accessing the database (scala) to do most of the work.
Insert all locations and then select all locations (2 queries)
Replace location with location id in persons list
Insert phone numbers and then select all phone numbers (2 queries)
Create a map of phone number's number to id
Insert persons list and then select persons id and name (2 queries)
Create a map of person's name to id
Create a new list of person_id, phone_number_id from the phone_numbers list and the persons map
Insert the new list (1 query)
The question I am asking can be broken into two parts:
How can I insert into two tables where one table requires a generated id from the other?
How can I insert a many to many relationship for two tables when the ids are generated on insert?
Ideally I would like to push all of this logic down to the database where I wont be wasting memory sending extra information between the driver and the database
I have to create a table in sql where one of the columns stores awards for a movie. The schema says it should store something like Oscar, screenplay. Is it possible to store two values in the same field in SQL. If so what datatype would that be and how would you query the table for it?
It's a horrible design pattern to store more than one piece of data in a single column in a relational database. The exact design of your system depends on several things, but here is one possible way to model it:
CREATE TABLE Movie_Awards (
movie_id INT NOT NULL,
award_id INT NOT NULL,
CONSTRAINT PK_Movie_Awards PRIMARY KEY CLUSTERED (movie_id, award_id)
)
CREATE TABLE Movies (
movie_id INT NOT NULL,
title VARCHAR(50) NOT NULL,
year_released SMALLINT NULL,
...
CONSTRAINT PK_Movies PRIMARY KEY CLUSTERED (movie_id)
)
CREATE TABLE Awards (
award_id INT NOT NULL,
ceremony_id INT NOT NULL,
name VARCHAR(50) NOT NULL, -- Ex: Best Picture
CONSTRAINT PK_Awards PRIMARY KEY CLUSTERED (award_id)
)
CREATE TABLE Ceremonies (
ceremony_id INT NOT NULL,
name VARCHAR(50) NOT NULL, -- Ex: "Academy Awards"
nickname VARCHAR(50) NULL, -- Ex: "Oscars"
CONSTRAINT PK_Ceremonies PRIMARY KEY CLUSTERED (ceremony_id)
)
I didn't include Foreign Key constraints here, but hopefully they should be pretty obvious.
Anything's possible; that doesn't mean it's a good idea :)
Far better to normalize your structure and store types like so:
AwardTypes:
AwardTypeID
AwardTypeName
Movies:
MovieID
MovieName
MovieAwardType:
MovieID
AwardTypeID
You can serialize your data in Json format,store Json string, and deselialize on read. More sefer than using your own format
Data presentation does't have to be so close tied with phisical data organisation. Wouldn't it be bether to store these two data in two separate columns and then just do some kind of concatenation at the display time?
It is much less painfull to join data than to split it, if you happen to need just a screenplay, one day...