SQL Server database diagram tool
One of the coolest hidden tools in SQL Server 2005 Express is Database Diagrams, a database-design tool that lets you visually lay out your database tables and their relationships. When you save your diagram, the tool generates all the database objects that you included. You can use the tool to create new database objects and to change the schema of existing objects.
Related: Report Builder and Tabular Model Databases
To get started using Database Diagrams, you'll need to use SQL Server Management Studio Express (SSMSE). To create a new database diagram, open SSMSE, then expand a database node. Beneath the database node, you'll see a Database Diagrams node. Initially this node will be empty, but you can create a new database diagram by right-clicking the node and selecting New Database Diagram from the context menu. Initially, you’ll see an Add Table dialog box that lets you add existing tables to your new diagram; this is how you’ll change the schema of existing tables.
To create a new set of tables, click Close on the Add Table dialog box. Then, right-click the design surface, and select New Table from the context menu. SSMSE prompts you for a table name, then the Table Designer appears. Enter the table's column names and their associated data types in the appropriate fields on the Table Designer. You can create one or more tables and drag connections between related columns. When you're finished creating a table, select Save Diagram from the File menu and enter the name of the diagram. Saving the diagram will create your new table.