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}.
Related
I am trying to create a simple SQLite database that will allow me to store email addresses and timestamps. I have created the table like this:
$sql =<<<EOF
CREATE TABLE ENTRIES
(ID INT PRIMARY KEY NOT NULL,
EMAIL EMAIL NOT NULL,
TIMESTAMP DATETIME DEFAULT CURRENT_TIMESTAMP);
EOF;
And I am trying to insert an email like this:
$sql =<<<EOF
INSERT INTO ENTRIES (EMAIL)
VALUES (test#test.com);
EOF;
I am getting an error
NOT NULL constraint failed: ENTRIES.ID
I am assuming this is to do with the ID and autoincrement? I have read the docs and it advises against using autoincrement. Where am I going wrong?
The docs say:
If a table contains a column of type INTEGER PRIMARY KEY, then that column becomes an alias for the ROWID.
And because it becomes an alias for the ROWID, it's not necessary to explicitly specify a value.
You have INT PRIMARY KEY, not INTEGER PRIMARY KEY. If you change it to INTEGER PRIMARY KEY, it works the way you expect.
I am working on an event management project. In that project, I have a form in admin panel as add event which contains events name, category, sub-category, event admin etc and more. And in the database, I have different tables like event category, event sub-category.
And also I have a table that is cultural event which includes form fields and foreign key. I pass event catid, event sub-cat id.
On button click that cultural event is added.
I want to insert data in their tables and I want id that I gave in cultural event table.
On single click I want to insert this
How can I achieve this? Using a stored procedure?
CREATE TABLE EVENT_SCAT (ESUBCAT_ID INT NOT NULL PRIMARY KEY, ECAT_ID INT NOT NULL FOREIGN KEY REFERENCES EVENT_CAT(ECAT_ID), ESUBCAT_NAME VARCHAR(255) NOT NULL, )
create table EVENT_CAT (ECAT_ID INT NOT NULL IDENTITY PRIMARY KEY, ECAT_NAME VARCHAR(255)NOT NULL, EID INT NOT NULL FOREIGN KEY REFERENCES EVENTDETAILS(EID)
CREATE TABLE Cultural_E (c_ID INT NOT NULL IDENTITY PRIMARY KEY, cEVENT_NAME VARCHAR(255) NOT NULL, cE_SDATE DATE NOT NULL, cE_EDATE DATE NOT NULL, SE_RULES1 VARCHAR(MAX), SE_RULES2 VARCHAR(MAX), SE_RULES3 VARCHAR(MAX), cE_RULES4 VARCHAR(MAX), cE_EFEES INT, EID INT NOT NULL FOREIGN KEY REFERENCES EVENTDETAILS(EID), ECAT_ID INT NOT NULL FOREIGN KEY REFERENCES EVENT_CAT(ECAT_ID) )
and i have form in asp.net which includes all fields in single form but there are different tables with foreign keys. and i want id of ecat id and subcatid in last table i.e Cultural_e.
for ex:THESE ARE TABLE
eVENT_T
ID ENAME EADMIN
1 CULTURAL NIKHIL
E_CAT
ID ECAT_NAME E_iD
1 SINGING 1
event_scat
ID eCAT_iD ESUBCAT_NAME
1 1 SOLO
NOW I HAVE TABLE THAT IS CULTURAL_T
THESE TABLE HAVE ITS OWN FILEDS AS WELL AS FOREIGN KEY LIKE EID ,ECAT_ID AS YOU CAN SEE ABOVE
AND I HAVE FORM IN ASP.NET AND FORM CONTAINS TEXTBOX TO ENTER DATA OF ALL THESE TABLE.
SO PLZ TELL ME HOW TO ACHIEVE THIS
THANK YOU
As per my understanding of your question,try to use triggers rather than stored procedures if possible.
CREATE TRIGGER InsertEvents
AFTER INSERT ON EVENT_CAT
BEGIN
/* Insert Query to EVENT_SCAT */
/* Insert Query to cultural */
END
I'm designing a new database for a company, trying to keep strict constraints with foreign keys etc for integrity. I have a table [Member] which holds companies on the system. This table has a column of [internalContact] for the user in our company who deals with this member which has a foreign linked to the users table by user id.
What I would like to know is if it is possible to assign a condition to the foreign key, since the users table contains internal and external users. ie. for the field to only accept a user id where the user type is 5. Can this be done, or can I only control this in my application code?
Thanks
You can use a check constraint for this.
(The code is untested some syntax errors will be in there)
CREATE TABLE Member
(
P_Id int NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255),
InternalContactId
CONSTRAINT chk_Person CHECK (isInternalUser(internalContactId) > 0)
)
ALTER TABLE Member
ADD FOREIGN KEY (InternalContacId)
REFERENCES Persons(P_Id)
Then just create a function isInternalUser that returns 1 if user in ok to be an internal contact
CREATE FUNCTION isInternalUser ( #userId int(10) )
RETURNS int
AS
BEGIN
DECLARE #tmp int
SELECT #tmp = count(*)
FROM users
WHERE userId = #UserId and <check to see if user is internal>
RETURN(#CtrPrice)
END
GO
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)
I have 2 tables as follows:
create table Users
(
UserId int primary key identity not null
)
create table UserExternalKeys
(
UserIdRef int primary key not null,
ExternalKey varchar(50) unique not null
)
alter table UserExternalKeys
add constraint fk_UsersExternalKeys_Users
foreign key (UserIdRef)
references Users (UserId)
Each user can have a 0 or 1 external keys. Things are setup this way because adding a nullable unique column to SQL Server does not allow for more than 1 null value.
Based on Ayende's post, it seems like this could be handled using a <one-to-one> mapping. However, this would require the UserExternalKeys table to have its own primary key.
The new schema would look something like this:
create table Users
(
UserId int primary key identity not null,
ExternalKeyRef int null
)
create table UserExternalKeys
(
UserExternalKeyId int primary key identity not null,
ExternalKey varchar(50) unique not null
)
alter table Users
add constraint fk_Users_UsersExternalKeys
foreign key (ExternalKeyRef)
references UserExternalKeys (UserExternalKeyId)
I think this would work, but it feels like I would only be adding the UserExternalKeyId column to appease NHibernate.
Any suggestions?
If a user can have 0 or 1 external keys why not design the tables as:
create table Users
(
UserId int primary key identity not null
ExternalKey varchar(50) null
)
and use one of the known workarounds for this problem. If you're using SQL Server 2008 you can use a filtered index. If you're using an earlier version you can use a trigger, an indexed view (2005), or the nullbuster workaround.
You could also keep your original schema and map the relationship as one-to-many from Users to UserExternalKeys. Map the collection as a private member and expose access to it through a property:
private IList<UserExternalKeys> _externalKeys;
public string ExternalKeys
{
get
{
if (_externalKeys.Count() == 1)
{
return _externalKeys.ElementAt(0).ExternalKey;
}
else
{
// return null or empty string if count = 0, throw exception if > 1
}
}
set
{
if (_externalKeys.Count() == 0) { // add key and set value }
else { // set value if count = 1, throw exception if > 1 }
}
}