CopyDatabaseDiagram.sql

DECLARE @values nvarchar(max);
SET @values = 
(
    SELECT '
        (''' + REPLACE(name, '''', '''''') + ''', ' + CAST(principal_id AS VARCHAR(100)) +', ' + CAST(version AS VARCHAR(100)) + ', ' + sys.fn_varbintohexstr(definition) + '),'
    FROM sysdiagrams
    FOR XML PATH(''), TYPE
).value('.', 'nvarchar(max)');
SET @values = LEFT(@values, LEN(@values) - 1);

SELECT
'IF OBJECT_ID(N''dbo.sysdiagrams'') IS NULL
    CREATE TABLE dbo.sysdiagrams
    (
        name sysname NOT NULL,
        principal_id int NOT NULL,
        diagram_id int PRIMARY KEY IDENTITY,
        version int,

        definition varbinary(max)
        CONSTRAINT UK_principal_name UNIQUE
        (
            principal_id,
            name
        )
    );

MERGE sysdiagrams AS Target
    USING
    (
        VALUES' + @values + '
    ) AS Source (name, principal_id, version, definition)
    ON Target.name = Source.name
        AND Target.principal_id = Source.principal_id
    WHEN MATCHED THEN
        UPDATE SET version = Source.version, definition = Source.definition
    WHEN NOT MATCHED BY Target THEN
        INSERT (name, principal_id, version, definition)
        VALUES (name, principal_id, version, definition);
';

--Copy the output and save as new .sql file. Run it to insert the Database Diagram.