Sub queries in check constraint

Note, what you really want is a foreign key constraint. That said, to get a "query" into a check you can write a function that contains the query and outputs a scalar value, then use that function in the check constraint.

CREATE FUNCTION myFunction (
    @field DATATYPE(?)
)
RETURNS VARCHAR(5)
AS
BEGIN
    IF EXISTS (SELECT* FROM Table2 WHERE MYFIELD = @field)
        return 'True'
    return 'False'
END

Something like that. Not tested.

Then you can add it to your check like so

ALTER TABLE Table1
    WITH CHECK ADD CONSTRAINT CK_Code
    CHECK (myFunction(MYFIELD) = 'True')

You can't have sub queries inside check constraints. What you can do is use a UDF that returns a scalar value inside the check constraint.

Step 1: Create the table

USE CTBX
GO

CREATE TABLE RawMaterialByGender 
(
RMGID int primary key identity(1,1),
RMID smallint foreign key references RawMaterialMaster(RMID),
LeveLMasterID smallint foreign key references LevelMaster(LevelTextID),
IsDeleted bit
)

Step 2 : Create the UDF that returns a scalar

Create FUNCTION [dbo].[IsValidLevelMasterGender](@LevelMasterID smallint)

    RETURNS bit
    AS
    BEGIN
     DECLARE @count smallint;
     DECLARE @return bit;

     SELECT @count = count(LevelTextID)      
     FROM [LevelMaster]
     WHERE LevelCategoryID = 3 AND IsActive = 1 AND LevelTextID=@LevelMasterID

     IF(@count = 0)
     SET @return = 'false';
     ELSE
     SET @return = 'true';

     RETURN @return;

    END;
    GO

Step 3 : Alter table to add the CHECK constraint

ALTER TABLE RawMaterialByGender 
ADD CONSTRAINT check_LevelMasterID CHECK (dbo.IsValidLevelMasterGender(LeveLMasterID) = 'true')

ALTER TABLE Table1
ADD CONSTRAINT FK_Table1_Code FOREIGN KEY (MyField)
REFERENCES Table2 (Field) ;

Ref: http://msdn.microsoft.com/en-us/library/ms190273.aspx
Note: I haven't checked the above for syntax.

First of all in your example you clearly need FK Constraint.

Another posibility is to use view with WITH CHECK OPTION and give access to user through it:

CREATE TABLE Table1(i INT PRIMARY KEY, CK_Code CHAR(1));
CREATE TABLE Table2(Field CHAR(1));
INSERT INTO Table2(Field) VALUES ('A'),('B'), ('C');
GO

CREATE VIEW v_Table1
AS
SELECT *
FROM Table1
WHERE CK_code IN (SELECT Field FROM Table2)  -- here goes your subquery check
WITH CHECK OPTION;

When you try to insert data that violates your "constraint" like:

INSERT INTO v_Table1(i, CK_Code)
VALUES(10, 'D');

You will get:

The attempted insert or update failed because the target view either specifies WITH CHECK OPTION or spans a view that specifies WITH CHECK OPTION and one or more rows resulting from the operation did not qualify under the CHECK OPTION constraint.

The statement has been terminated.

LiveDemo

Sub queries in check constraint

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