I have a table in SQL server that accepts either a true or false value. Is there anyway to say that it can be true or false and not a fixed value. My table is for a container that can hold hot food or cold food. I want some of the containers to be able to carry hot or cold food depending on an order.
SQL Server has Bit type. Try Something like this:
CREATE TABLE yourtablename
(
ID int PRIMARY KEY,
IsHot bit not null default 1
)
Did you try check constraint?
Example code:
CREATE TABLE dbo.Vendors
(VendorID int PRIMARY KEY, VendorName nvarchar (50),
CreditRating tinyint)
GO
ALTER TABLE dbo.Vendors ADD CONSTRAINT CK_Vendor_CreditRating
CHECK (CreditRating >= 1 AND CreditRating <= 5)
This this example we're forcing column CreditRating to store values from 1 to 5. Hope this helps.
Related
I'm doing a school project about a school theme where I need to create some tables for Students, Classes, Programmes...
I want to add a Group to determined classes with an auto increment in group_id however I wanted the group_id variable to reset if I change any of those attributes(Classes_id,courses_acronym,year_Semesters) how can I reset it every time any of those change??
Here is my table:
CREATE TABLE Classes_Groups(
Classes_id varchar(2),
Group_id INT IDENTITY(1,1),
courses_acronym varchar(4),
year_Semesters varchar(5),
FOREIGN KEY (Classes_id, year_Semesters,courses_acronym) REFERENCES Classes(id,year_Semesters, courses_acronym),
PRIMARY KEY(Classes_id,courses_acronym,year_Semesters,Group_id)
);
Normally, you do not (need to) reset the identity column of a table. An identity column is used to create unique values for every single record in a table.
So you want to generate entries in your groups table based on new entries in your classes table. You might create a trigger on your classes table for that purpose.
Since Group_id is already unique by itself (because of its IDENTITY), you do not need other fields in the primary key at all. Instead, you may create a separate UNIQUE constraint for the combination (Classes_id, courses_acronym, year_Semesters) if you need it.
And if the id field of your classes table is an IDENTITY column too, you could define a primary key in your classes table solely on that id field. And then your foreign key constraint in your new groups table can only include that Classes_id field.)
So much for now. I guess that your database design needs some more additional tuning and tweaking. ;)
where are you setting the values from?, you can have a stored proc and in your query have the columns have an initial value set when stored proc is hit assuming there are values at the beginning
.Then use an IF statement.
declare #initial_Classes_id varchar(2) = --initial value inserted
declare #initial_courses_acronym varchar(4) = --initial value inserted
declare #initial_year_Semesters varchar(5) = --initial value inserted
declare #compare_Classes_id varchar(2) = (select top 1 Classes_id from Classes_Groups order by --PK column desc for last insert); l would add Dateadded and then order with last insert date
declare #compare_courses_acronym varchar(2) = (select top 1 Classes_id from Classes_Groups where Classes_id = #compare_Classes_id);
declare #compare_year_Semesters varchar(2) = (select top 1 Classes_id from Classes_Groups where Classes_id = #compare_Classes_id);
IF (#initial_Classes_id != #compare_Classes_id OR #initial_courses_acronym != #compare_courses_acronym OR #initial_year_Semesters != #compare_year_Semesters)
BEGIN
DBCC CHECKIDENT ('Group_id', RESEED, 1)
Insert into Classes_Groups (courses_acronym,year_Semesters)
values (
courses_acronym,
year_Semesters
)
END
ELSE
BEGIN
Insert into Classes_Groups (courses_acronym,year_Semesters)
values (
courses_acronym,
year_Semesters
)
END
NB: would advice to use int on the primary key. Unless you have a specific purpose of doing so.
i am not sure if i could use conditional statement while creating new columns.
Code:
create table Employees(
Emp_ID int primary key identity (1,1),
Hours_worked int,
Rate int default '')
/*Now here in default value i want to set different rates depending upon hours worked. like if hour worked is greater than 8 then rate is 300, if hours worked is less than 8 hour the rate is 200.) How to write this as a Default value in sql server 2008.
My second question is:
Why i get error if i write like this,
create table tbl_1(
col_1 varchar(max) unique
)
The error is
Column 'col_1' in table 'tbl_1' is of a type that is invalid for use as a key column in an index.
Msg 1750, Level 16, State 0, Line 1
Regards
Waqar
you can use COMPUTED Column, http://msdn.microsoft.com/en-us/library/ms191250.aspx
create table Employees(
Emp_ID int primary key identity (1,1),
Hours_worked int,
Rate as (case when Hours_worked > 8 then 300 else 200 end) persisted )
The default value cannot refer to any other column names. So the "default" value of Rate won't know the value of Hours_worked. You could handle it with a trigger or whatever is doing the actual inserting could contain this logic.
http://msdn.microsoft.com/en-us/library/ms173565(v=sql.100).aspx
You cannot but a UNIQUE constraint on a VARCHAR(MAX) field.
I have like 11 columns in my database table and i am inserting data in 10 of them. i want to have a unique number like "1101 and so on" in the 11th column.
Any idea what should i do?? Thanks in advance.
SQL Server 2012 and above you can generate Sequence
Create SEQUENCE RandomSeq
start with 1001
increment by 1
Go
Insert into YourTable(Id,col1...)
Select NEXT VALUE FOR RandomSeq,col1....
or else you can use Identity
Identity(seed,increment)
You can start the seed from 1101 and increment the sequence by 1
Create table YourTable
(
id INT IDENTITY(1101,1),
Col varchar(10)
)
If you want to have that unique number in a different field then you can manipulate that field with primary key and insert that value.
If you want in primary key value, then open the table in design mode, go to 'Identity specification', set 'identity increment' and 'identity seed' as you want.
Alternatively you can use table script like,
CREATE TABLE Persons
(
ID int IDENTITY(12,1) PRIMARY KEY,
FName varchar(255) NOT NULL,
)
here the primary key will start seeding from 12 and seed value will be 1.
If you have your table definition already in place you can alter the column and add Computed column marked as persisted as:
ALTER TABLE tablename drop column column11;
ALTER TABLE tablename add column11 as '11'
+right('000000'+cast(ID as varchar(10)), 2) PERSISTED ;
--You can change the right operator value from 2 to any as per the requirements.
--Also replace ID with the identity column in your table.
create table inc
(
id int identity(1100,1),
somec char
)
Is it possible to insert 0 in the primary key field of a table in SQL server 2008?
As long it's a numeric field, yes... follow along at home!
create table TestTable
(
TestColumn int not null primary key
)
insert TestTable values(0)
The primary key restriction only requires that the value be unique and the column not be nullable.
For an identity field:
create table TestTable
(
TestColumn int identity(1, 1) not null primary key --start at 1
)
set identity_insert TestTable on
insert TestTable (TestColumn) values (0) --explicitly insert 0
set identity_insert TestTable off
The identity(1, 1) means "start at one and increment by one each time something is inserted". You could have identity(-100, 10) to start at -100 and increment by 10 each time. Or you could start at 0. There's no restriction.
You can generally answer questions like these for yourself by just trying them and seeing if they work. This is faster and usually more beneficial than asking on StackOverflow.
Yes, it can be zero. The value can be from −2,147,483,648 to 2,147,483,647, from −(2^31) to 2^31 − 1, the full range of an unsigned integer.
If you expect a lot of records, like up to 4.3 billion, it makes sense to start from the smallest value, and work your way up.
CREATE TABLE TestTable
(
TestColumn INT IDENTITY(−2,147,483,648, 1) NOT NULL PRIMARY KEY --start at 1
)
How could I set a constraint on a table so that only one of the records has its isDefault bit field set to 1?
The constraint is not table scope, but one default per set of rows, specified by a FormID.
Use a unique filtered index
On SQL Server 2008 or higher you can simply use a unique filtered index
CREATE UNIQUE INDEX IX_TableName_FormID_isDefault
ON TableName(FormID)
WHERE isDefault = 1
Where the table is
CREATE TABLE TableName(
FormID INT NOT NULL,
isDefault BIT NOT NULL
)
For example if you try to insert many rows with the same FormID and isDefault set to 1 you will have this error:
Cannot insert duplicate key row in object 'dbo.TableName' with unique
index 'IX_TableName_FormID_isDefault'. The duplicate key value is (1).
Source: http://technet.microsoft.com/en-us/library/cc280372.aspx
Here's a modification of Damien_The_Unbeliever's solution that allows one default per FormID.
CREATE VIEW form_defaults
AS
SELECT FormID
FROM whatever
WHERE isDefault = 1
GO
CREATE UNIQUE CLUSTERED INDEX ix_form_defaults on form_defaults (FormID)
GO
But the serious relational folks will tell you this information should just be in another table.
CREATE TABLE form
FormID int NOT NULL PRIMARY KEY
DefaultWhateverID int FOREIGN KEY REFERENCES Whatever(ID)
From a normalization perspective, this would be an inefficient way of storing a single fact.
I would opt to hold this information at a higher level, by storing (in a different table) a foreign key to the identifier of the row which is considered to be the default.
CREATE TABLE [dbo].[Foo](
[Id] [int] NOT NULL,
CONSTRAINT [PK_Foo] PRIMARY KEY CLUSTERED
(
[Id] ASC
) ON [PRIMARY]
) ON [PRIMARY]
GO
CREATE TABLE [dbo].[DefaultSettings](
[DefaultFoo] [int] NULL
) ON [PRIMARY]
GO
ALTER TABLE [dbo].[DefaultSettings] WITH CHECK ADD CONSTRAINT [FK_DefaultSettings_Foo] FOREIGN KEY([DefaultFoo])
REFERENCES [dbo].[Foo] ([Id])
GO
ALTER TABLE [dbo].[DefaultSettings] CHECK CONSTRAINT [FK_DefaultSettings_Foo]
GO
You could use an insert/update trigger.
Within the trigger after an insert or update, if the count of rows with isDefault = 1 is more than 1, then rollback the transaction.
CREATE VIEW vOnlyOneDefault
AS
SELECT 1 as Lock
FROM <underlying table>
WHERE Default = 1
GO
CREATE UNIQUE CLUSTERED INDEX IX_vOnlyOneDefault on vOnlyOneDefault (Lock)
GO
You'll need to have the right ANSI settings turned on for this.
I don't know about SQLServer.But if it supports Function-Based Indexes like in Oracle, I hope this can be translated, if not, sorry.
You can do an index like this on suposed that default value is 1234, the column is DEFAULT_COLUMN and ID_COLUMN is the primary key:
CREATE
UNIQUE
INDEX only_one_default
ON my_table
( DECODE(DEFAULT_COLUMN, 1234, -1, ID_COLUMN) )
This DDL creates an unique index indexing -1 if the value of DEFAULT_COLUMN is 1234 and ID_COLUMN in any other case. Then, if two columns have DEFAULT_COLUMN value, it raises an exception.
The question implies to me that you have a primary table that has some child records and one of those child records will be the default record. Using address and a separate default table here is an example of how to make that happen using third normal form. Of course I don't know if it's valuable to answer something that is so old but it struck my fancy.
--drop table dev.defaultAddress;
--drop table dev.addresses;
--drop table dev.people;
CREATE TABLE [dev].[people](
[Id] [int] identity primary key,
name char(20)
)
GO
CREATE TABLE [dev].[Addresses](
id int identity primary key,
peopleId int foreign key references dev.people(id),
address varchar(100)
) ON [PRIMARY]
GO
CREATE TABLE [dev].[defaultAddress](
id int identity primary key,
peopleId int foreign key references dev.people(id),
addressesId int foreign key references dev.addresses(id))
go
create unique index defaultAddress on dev.defaultAddress (peopleId)
go
create unique index idx_addr_id_person on dev.addresses(peopleid,id);
go
ALTER TABLE dev.defaultAddress
ADD CONSTRAINT FK_Def_People_Address
FOREIGN KEY(peopleID, addressesID)
REFERENCES dev.Addresses(peopleId, id)
go
insert into dev.people (name)
select 'Bill' union
select 'John' union
select 'Harry'
insert into dev.Addresses (peopleid, address)
select 1, '123 someplace' union
select 1,'work place' union
select 2,'home address' union
select 3,'some address'
insert into dev.defaultaddress (peopleId, addressesid)
select 1,1 union
select 2,3
-- so two home addresses are default now
-- try adding another default address to Bill and you get an error
select * from dev.people
join dev.addresses on people.id = addresses.peopleid
left join dev.defaultAddress on defaultAddress.peopleid = people.id and defaultaddress.addressesid = addresses.id
insert into dev.defaultaddress (peopleId, addressesId)
select 1,2
GO
You could do it through an instead of trigger, or if you want it as a constraint create a constraint that references a function that checks for a row that has the default set to 1
EDIT oops, needs to be <=
Create table mytable(id1 int, defaultX bit not null default(0))
go
create Function dbo.fx_DefaultExists()
returns int as
Begin
Declare #Ret int
Set #ret = 0
Select #ret = count(1) from mytable
Where defaultX = 1
Return #ret
End
GO
Alter table mytable add
CONSTRAINT [CHK_DEFAULT_SET] CHECK
(([dbo].fx_DefaultExists()<=(1)))
GO
Insert into mytable (id1, defaultX) values (1,1)
Insert into mytable (id1, defaultX) values (2,1)
This is a fairly complex process that cannot be handled through a simple constraint.
We do this through a trigger. However before you write the trigger you need to be able to answer several things:
do we want to fail the insert if a default exists, change it to 0 instead of 1 or change the existing default to 0 and leave this one as 1?
what do we want to do if the default record is deleted and other non default records are still there? Do we make one the default, if so how do we determine which one?
You will also need to be very, very careful to make the trigger handle multiple row processing. For instance a client might decide that all of the records of a particular type should be the default. You wouldn't change a million records one at a time, so this trigger needs to be able to handle that. It also needs to handle that without looping or the use of a cursor (you really don't want the type of transaction discussed above to take hours locking up the table the whole time).
You also need a very extensive tesing scenario for this trigger before it goes live. You need to test:
adding a record with no default and it is the first record for that customer
adding a record with a default and it is the first record for that customer
adding a record with no default and it is the not the first record for that customer
adding a record with a default and it is the not the first record for that customer
Updating a record to have the default when no other record has it (assuming you don't require one record to always be set as the deafault)
Updating a record to remove the default
Deleting the record with the deafult
Deleting a record without the default
Performing a mass insert with multiple situations in the data including two records which both have isdefault set to 1 and all of the situations tested when running individual record inserts
Performing a mass update with multiple situations in the data including two records which both have isdefault set to 1 and all of the situations tested when running individual record updates
Performing a mass delete with multiple situations in the data including two records which both have isdefault set to 1 and all of the situations tested when running individual record deletes
#Andy Jones gave an answer above closest to mine, but bearing in mind the Rule of Three, I placed the logic directly in the stored proc that updates this table. This was my simple solution. If I need to update the table from elsewhere, I will move the logic to a trigger. The one default rule applies to each set of records specified by a FormID and a ConfigID:
ALTER proc [dbo].[cpForm_UpdateLinkedReport]
#reportLinkId int,
#defaultYN bit,
#linkName nvarchar(150)
as
if #defaultYN = 1
begin
declare #formId int, #configId int
select #formId = FormID, #configId = ConfigID from csReportLink where ReportLinkID = #reportLinkId
update csReportLink set DefaultYN = 0 where isnull(ConfigID, #configId) = #configId and FormID = #formId
end
update
csReportLink
set
DefaultYN = #defaultYN,
LinkName = #linkName
where
ReportLinkID = #reportLinkId