Create a Database Model (also known as Entity Relationship diagram) - Visio
It is a common task for a developer to build an Entity Relationship (ER) Diagram for an existing database. If you are dealing with an MS SQL. This section of notes covers how to draw Entity Relationship Diagrams with Crow's Foot Notation using Microsoft Visio While there are many purpose- built. I want draw a ER Diagram. how do i do that? i haven't a database to link. http:// az-links.info
For example, you can type decimal 8,2 or char To prevent null values, select the Req'd check box. To specify that the column is a primary key, select the PK check box. To see more column properties in addition to those that appear when you click the Columns category, select the column and then click Edit. Relationships Relationships use primary and foreign keys to allow databases to match a row in one table with a row in a related table. You can show those relationships in your diagram.
In addition, you can set their cardinality for example, one-to-many and use either Crow's feet, Relational, or IDEF1X notation to show the cardinality. You can't show many-to-many relationships with any of these notations in the Database Model Diagram template. Create a relationship between tables: Make sure that both tables are visible in the diagram. If you reverse engineered the model from an existing database, you may need to drag one or both from the Tables and Views window onto the drawing page.
Drawing E-R Diagrams with Crow's Foot Notation using Microsoft Visio Full Tutorial
Double-click the table that you want for the primary key side of the relationship. In the grid, click the column that you want to use to uniquely identify each row in the table, and select the PK check box to set it as the primary key.
From the Object Relational or Entity Relationship stencil, drag a Relationship shape and drop it onto a blank space on the page. Connect the higher end to the table with the parent table. Connect the other end to the child table. If the second table doesn't already contain a column with the same name as the primary key, the modeler adds it to the second table as a foreign key.
If relationship lines disappear, on the Database tab, in the Manage group, click Display Options. On the Relationships tab, under Show, select the Relationships check box. Set the relationship's cardinality: In the Database Properties window, under Categories, click Miscellaneous.
Under Cardinality, choose the cardinality that best fits the relationship. For one-to-many relationships, the best choice is either Zero or more or One or more. For one-to-one relationships, the best choice is either Zero or one or Exactly one.
To make other refinements to your diagram such as creating indexes, check clauses, and triggers you can do the following: Create indexes Indexes improve the performance, or speed, of your database when you run a query.
Open the database model diagram. Double-click the table to which you want to add an index, and in the Database Properties window, in the Categories list, click Indexes.
In the Create Index dialog box, type a name for the index, and then click OK. In the Index Type list, select an option to create a unique or non-unique index. In the Indexed Columns list, select the Asc check box to create an index that has an ascending sort order, or clear the check box to create an index that has a descending sort order. The database model diagram is updated. Create views You can think of a view as a saved query.
Views are particularly handy if you need to repeatedly access the same information from multiple tables, or if you want to expose the data to users without letting them change the actual tables.
Creating Entity Relationship Diagram in Visio
Set extended properties for tables and views Depending on your database management system DBMSyou may be able to set extended properties for tables or views to determine where they are stored. Double-click the table or view whose extended properties you want to set, and in the Database Properties window, in the Categories list, click Extended. Create check clauses Use check clauses to ensure that the data that is entered into a column is within a particular range of values.
For example, you can create a check clause that requires the data in a column called "Age" to be over Double-click the table to open the Database Properties window. Under Categories, click Columns and then click the column that you want to add a check clause to. On the Check tab of the Column Properties dialog box, enter the constraints that you want.
Create a Database Model (also known as Entity Relationship diagram)
The check clause is added to the Code window under Local code. Create stored procedures and user-defined functions Use stored procedures and user-defined functions to create packets of code that you can reuse to perform the same actions repeatedly. The major difference between the two is that a user-defined function returns a value, whereas the stored procedure executes code without returning a value.
Click Global Code and then click New. On the Properties tab of the Code Editor, click the kind of code that you want to create, and type a name for the code. On the Body tab, type the code and then click OK. Create triggers Triggers cause SQL code that you specify in the trigger to run when a particular event occurs in the database.
Under Categories, click Triggers, and then click Add. On the Properties tab, type a name for the trigger. The trigger is added to the Code window under Local code. Can't find the database model features? Most likely, your edition of Microsoft Office Visio doesn't include the features that you are looking for.
The name of the edition is in the top line of text in the dialog box. Microsoft Office Visio Professional supports the reverse engineering features for the Database Model Diagram template that is, using an existing database to create a model in Visiobut it does not support forward engineering that is, using a Visio database model to generate SQL code.
You can find the full suite of database modeling features, including both reverse engineering and forward engineering, in Visio for Enterprise Architects. On the Database menu, point to Options, and then click Document. If you are reverse engineering a Microsoft Office Excel workbook, before you start the wizard you need to open the workbook and name the group or range of cells that contains the column headings.
For more information about how to name a range of cells, see the topic in your Microsoft Office Excel help titled Define named cell references or ranges. On the Database menu, click Reverse Engineer. For example, in the Connect Data Source dialog box, type a user name and password, and then click OK. You can also lay things out in the way that you want, and catch changes made to the database.
The key here is to create a connection to your database. It does not have to be a Microsoft database. Most likely, if there is an ODBC Data Source defined on your computer, you can connect to your database in Visio and generate the diagram.
The process would be similar for connecting to other types of databases. Usually, you do not have to do this for Access Database. It should have been created when Office or Visio is installed.
For other types of databases, you may need to first install an ODBC Driver which is often available from your database provider. It is important to choose the right template, or you will not see the feature we want to use. Once the file is created, you will see two new things that you normally do not see.
Please note that you will not see them, if you did not choose the right template in step 2. Then you will be asked for user credential.