In my TSQL table I added a constraint with the following sQL statement
alter table disabledqualities
add constraint uc_uIdQualCode
unique (userId, qualitycode)
I did it by hand because I just can't work out how the GUI is supposed to work.
You add a constraint and then you get a window where you should "define" your constraint. It's basically just a textbox. And no matter what I seem to enter, it never validates..
What am I supposed to enter in the box?
you would use new index not new constraint to add a unique constraint (read index)
new constraint is to add check constraints
in the new index window check unique
Example, column must be between 0 and 1,
((0)<=[TABLE].[COLUMN] AND [TABLE].[COLUMN]<=(1))
When adding unique constraints, it's actually an index, like primary key, so you click on indexes/keys.
Related
I want use a check constraint for a column in any table in SQL Server 2008.
I would like give a qualified name to the check constraint.
I have seen several syntax version on how to create it:
ALTER TABLE [dbo].[Roles2016.UsersCRM] WITH CHECK
ADD CHECK (([Estado]=(4) OR [Estado]=(3) OR [Estado]=(2) OR [Estado]=(1)))
ALTER TABLE [dbo].[Roles2016.UsersCRM] WITH CHECK
ADD CONSTRAINT [CK_UsuariosCRM_Estado]
CHECK (([Estado]=(4) OR [Estado]=(3) OR [Estado]=(2) OR [Estado]=(1)))
What's difference ADD CHECK and ADD CONSTRAINT for a check constraint?
It is possible, but a very bad habit to add constraints without a name:
CREATE TABLE tbl(SomeColumn VARCHAR(10) DEFAULT('test'))
will create a CONSTRAINT with a random name. Better use this
CREATE TABLE tbl(SomeColumn VARCHAR(10) CONSTRAINT DF_YourTable_SomeColumm DEFAULT('test'))
This will do the same, but will name the constraint like you want it.
This is extremely important if you run upgrade scripts in deployed environments. Just imagine, you want to change a constraint later and the name of this constraint is all different on your customers machines... That's a real pain!
So: Always name your constraints!
I need your help...., Please help me
I want to add a new primary key to an existing table which already has 3 columns as composite primary key. But, I do not want to drop the old primary key, since there are many records and the old primary key also have relationship with other table
When I am using this query:
alter table hem154
add indexNO uniqueidentifier default newid()
alter table hem154
add CONSTRAINT pk_hem154_indexNo PRIMARY KEY (PK_indexNO)
Note:
Hem154 ~ Table Name
indexNo ~ Column Name which will to added
I get this runtime error:
Msg 1779, Level 16, State 0, Line 1
Table 'hem154' already has a primary key defined on it.
Msg 1750, Level 16, State 0, Line 1
Could not create constraint. See previous errors.
Please help me, how can I do it???
Thanks
Drop all primary keys and add Again all primary keys
ALTER TABLE hem154
DROP PRIMARY KEY,ADD PRIMARY KEY (col1,col2,indexNO);
You can only have one primary key per table. You can either add a second table that maps your new PK to the old PK, or drop the old PK and add the new one. Dropping the PK won't drop the columns, it just stops using them as the composite key. Any tables that were relying on the old key should probably be updated as well to support whatever answer you decide on.
First DROP existing PRIMARY KEY and ADD new composite PRIMARY KEY.
ALTER TABLE Table1
DROP CONSTRAINT PK_Table1_Col1
GO
and then try your code
There is no easy way of doing this. From your question, I understand that you want to add one additional column to the existing Primary Key. If they have existing relationships, then it is not possible to do this, without dropping those FK constraints first. Even if you do that, you will not be able to reestablish those FK constraints again, as you have modified the PK.
If you do not need to reestablish those FK relationships, then you can do this:
Drop all FK relationships
Drop existing PK (data will not be deleted, only the constraint will be dropped)
Add new column
Recreate PK to include the new column
However, if you cannot drop the existing FK constraints, then I am afraid this is not possible
On Microsoft SQL Server Management Studio:
Select/highlight both columns
Right click either
Press "Set primary key"
I have a column (which represents an e-mail) in a SQL Server database with varchar(50) as data type and I would like to make it unique (do not allow the same two e-mail addresses). I cannot find a way to make such column unique in SQL Server Management Studio.
How to do that?
In T-SQL it would be
ALTER TABLE MyTable WITH CHECK
ADD CONSTRAINT UQ_MyTable_Email UNIQUE (EmailAddress)
Or as an explicit index
CREATE UNIQUE INDEX IXU_Email ON MyTable (EmailAddress)
Edit: I can't see how to create a constraint in the SSMS GUI: other answers show how to manage indexes. I do only use SQL though, never the GUI for this kind of work
In the Object Explorer under the table right-click the Indexes folder and choose New Index....
In the window that appears enter Index name:, tick the Unique checkbox and add your email field from the Add... button then click OK.
Try this:
ALTER TABLE [dbo].[TableName] ADD CONSTRAINT UNQ__TableName__ColumnName UNIQUE ([ColumnName])
From this:
http://msdn.microsoft.com/en-us/library/ms191166.aspx
I love foreign keys, but I'm running into one problem with them. I have a conversion program where I am disabling foreign keys to tables. The reason I'm doing this is so that I can reconvert all records in the main table, but leave the other tables dependent on that one untouched without having to reconvert them every time because they are HUGE.
I'm using these commands to disable and re-enable the foreign keys:
ALTER TABLE MyTable NOCHECK CONSTRAINT MyConstraint
ALTER TABLE MyTable CHECK CONSTRAINT MyConstraint
However, after I re-enable the constraint "Check Existing Data on Creation or Re-Enabling" is still set to No. I understand that it is set to No because I disabled the constraint, but by doing this it altered my database schema, which I don't like. I thought this would be considered re-enabling the constraint and would check the existing data, but apparently not.
Is there no way to change this with the ALTER TABLE command? I know I can if I drop the constraint and recreate it, but I'm not about to write the script to recreate every foreign key I have and maintain that.
I'm using SQL Server 2008 R2.
To re-enable a constraint:
-- Enable the constraint
ALTER TABLE MyTable
WITH CHECK CHECK CONSTRAINT MyConstraint
GO
Note: you have to specify CHECK twice to force a check that all foreign key values are valid.
FOREIGN KEY and CHECK constraints that are disabled are marked
is_not_trusted.These are viewable in the sys.check_constraints and
sys.foreign_keys catalog views. This means that the constraint is no
longer being verified by the system for all rows of the table. Even
when you re-enable the constraint, it will not reverify the existing
rows against the table unless you specify the WITH CHECK option of
ALTER TABLE. Specifying WITH CHECK marks the constraint as trusted
again.
Ref.: Guidelines for Disabling Indexes and Constraints
As noted in comments (for search engines), this corresponds to
sys.foreign_keys.is_not_trusted
in the catalog view
I have a table in my database and I did a: Script table as > Create to > query editor and some of my columns have this code:
ALTER TABLE [dbo].[TableName] WITH CHECK ADD CONSTRAINT [ConstraintName] FOREIGN KEY([ColumnName])
REFERENCES [dbo].[ForeignKeyTable] ([ColumnName])
GO
ALTER TABLE [dbo].[TableName] CHECK CONSTRAINT [ConstraintName2]
GO
What does the second constraint do? Other columns in the table only have the first constraint.
The second constraint turns on (activates) the check constraint. It is just template code from SSMS
It is possible to generate the create check constraints snippet with or without activating it (e.g. nocheck) - so that is itself one of 2 snippets. Because you opted for the constraints to end up activated, SSMS follows with the activation, not really caring if it was activated already or not. It doesn't really hurt and is just something SSMS does