SQL Server 2008中的正则表达式

Question

How to write this check constraint:

, varchar column with nonempty strings consisting of A's or B's.

Some constraints do work, this simple doesn't.
Problem with collation, or something?

Answer 1

SQL server does not natively support Regex.

However, it is possible to add check constraint to match the pattern that you provided

not like '%[^AB]%'

Test:

declare @Test table(TestColumn varchar(100) check (TestColumn not like '%[^AB]%' and TestColumn != ''))

insert @Test
values ('AABAB')  -- passed

insert @Test
values ('AAB')    -- passed

insert @Test
values ('AABC')   -- failed  

insert @Test
values ('')  -- failed

LIKE patterns are very limited. If you need true Regex constraints you could implement very simple CLR function. There are plenty examples in the internet. For example: Regular Expressions Make Pattern Matching And Data Extraction Easier .

Answer 2

SQL server 2008 doesn't support regular expressions natively. You can write a custom CLR user-defined function that does this. MSDN has a wealth of resources to guide you through the process of creating one. This article , for example.

Additionally, this article seems to cover exactly what you want to do with check constraints. It demonstrates how you can set a CLR UDF as your check constraint.

Answer 3

If you want to use a full functionality regex in MSSQL constraint - you need to write a custom dll and attach it to the sql server. then you will able to register it as a local function and use the regext any way you like.

see http://msdn.microsoft.com/en-us/library/w2kae45k(v=vs.80).aspx .

If you have diffuculties with this - I can post a simple example of working clr library for MSSQL

Answer 4

If using Check constraint given by others above (ie. [AB][AB] etc), does not give you the flexibility to test the varchar value properly then you could try using a trigger.

A trigger will allow you to test what your after more thoroughly.

Refer Example C on this link while its using the trigger to test business rules across tables its just a matter of changing it to suit what ever test you need to do :)

Hope this helps

Sample code to help you along change the testing to suit your needs

CREATE TABLE [dbo].[TestTrigger](
    [stringtest] [varchar](100) NULL
) ON [PRIMARY]
GO

CREATE TRIGGER [dbo].[TestTrigger_TestAB] 
    ON [dbo].[TestTrigger] 
    FOR INSERT,UPDATE
AS 
BEGIN
    SET NOCOUNT ON;

    DECLARE @testString varchar(100)
    Declare @Len as int;
    Declare @SearchPattern as varchar(8000);
    Declare @Result as Int;

    SELECT @testString = stringtest FROM inserted

    Select @Len = Len(@testString);

    While @Len>0
    Begin
        Select @SearchPattern = Isnull(@SearchPattern,'') + '[A-B]';
        Select @Len = @Len -1;
    End

    Select @Result = Case When @testString Like @SearchPattern Then 1 Else 0 End;

    IF (@Result = 0)
    BEGIN
        RAISERROR ('Value entered did not contain only A or B', 16, 1)
        ROLLBACK TRANSACTION
    END
END


SET ANSI_PADDING OFF
GO

Answer 5

SELECT * FROM t
WHERE REPLACE(REPLACE(col, 'A', ''), 'B', '') = ''