Using the ERD tool ================== The Entity-Relationship Diagram (ERD) tool is a database design tool that provides a graphical representation of database tables, columns, and inter-relationships. ERD can give sufficient information for the database administrator to follow when developing and maintaining the database. To access the ERD tool, select **Tools > ERD Tool**. The ERD tool allows you to: - Design and visualize the database tables and their relationships. - Add notes to the diagram. - Align the tables and links for a cleaner look. - Save the diagram and open it later to continue working on it. - Generate ready-to-run SQL from the database design. - Generate the database diagram for an existing database. .. figure:: /images/erd_tool.png :width: 70% :alt: ERD Tool ERD Tool You can open multiple copies of the ERD tool in individual tabs simultaneously. To close a copy of the ERD tool, select the **X** in the upper-right corner of the tab bar. Toolbar ------- The ERD Tool toolbar uses context-sensitive icons that provide shortcuts to frequently performed tasks. File options ------------ .. csv-table:: :header: Icon,Behavior,Shortcut :widths: 12,25,15 :align: left :class: longtable Open File,Load a saved diagram.,Ctrl + O Save,Save changes to a saved diagram or save the diagram to a file.,Ctrl + S Save as,Open a new dialog box and specify a new location to save the diagram.,Ctrl + Shift + S Export options -------------- .. csv-table:: :header: Icon,Behavior,Shortcut :widths: 12,25,15 :align: left :class: longtable Generate SQL,Generate the DDL SQL for the diagram and open a Query tool with the generated SQL ready for execution.,Option + Ctrl + S Download image,Save the ERD diagram in an image format.,Option + Ctrl + I Editing options --------------- .. csv-table:: :header: Icon,Behavior,Shortcut :widths: 12,25,15 :align: left :class: longtable Add table,"Add a new table to the diagram. In the table dialog box, enter the table details.",Option/Alt + Ctrl + A Edit table,"Edit a selected table on the diagram. In the table dialog box, enter the table details.",Option/Alt + Ctrl + E Clone table,"Clone the complete table structure, name it with a auto-generated name, and put it in the diagram.",Option/Alt + Ctrl + C Drop table/link,Drop a selected table or link.,Option/Alt + Ctrl + D Table relationship options -------------------------- .. csv-table:: :header: Icon,Behavior,Shortcut :widths: 12,25,15 :align: left :class: longtable 1M,Open a one-to-many relationship dialog box to add a relationship between two tables. The selected table is the referencing table and has the `many` endpoint of the link.,Option/Alt + Ctrl + O MM,Open a many-to-many relationship dialog box to add a relationship between two tables. This option creates a linked table from the selected columns of the two relating tables.,Option/Alt + Ctrl + M Utility Options --------------- .. csv-table:: :header: Icon,Behavior,Shortcut :widths: 12,25,15 :align: left :class: longtable Add/Edit note,Make notes on table nodes while designing the database.,Option/Alt + Ctrl + N Auto align,Align all tables and links for a cleaner look.,Option/Alt + Ctrl + L Show details,Toggle the column details. You can also choose to show few or more column details.,Option/Alt + Shift + D Zoom options ------------ .. csv-table:: :header: Icon,Behavior,Shortcut :widths: 12,25,15 :align: left :class: longtable Zoom to fit,Zoom in/out automatically and fit all the tables to the view.,Option/Alt + Shift + F Zoom in,Zoom in on the diagram.,"Option/Alt + Shift + ""+""" Zoom out,Zoom out on the diagram.,"Option/Alt + Shift + ""-""" Table dialog ------------ The table dialog box allows you to: - Change the table structure details. - Edit an existing table or add a new one. Table node ---------- The table node shows table details in a graphical representation: - On the top bar: - To show column details, select **Details toggle**. - When you add a note, **Note** becomes enabled. Select **Note** to changes notes. - The first row displays the table’s schema name, like ``public`` in the example. - The second row displays the table’s name, like ``users`` in the example. - The remaining rows dispalys the table’s column names and their data types. - A column that is a primary key displays as a lock key, like ``id integer`` in the example. - Other columns diplay as a green column, like ``email character varying`` in the example. - Select the node to drag it on the canvas. - To open the table dialog box and change the table details, either double-click the table node or select **Edit** on the toolbar. One-to-many link dialog box --------------------------- .. figure:: /images/erd_1m_dialog.png :width: 70% :alt: ERD Tool - One-to-Many Dialog Box ERD Tool - One-to-Many Dialog Box The one-to-many link dialog box allows you to: - Add a foregin key relationship between two tables. - Select a Local Table that references another table. The Local Table has the ``many`` end point. - Select a Local Column that references another column. - Select the Referenced Table. The Referenced Table has the ``one`` end point. - Select the Referenced Column. Many-to-many link dialog box ---------------------------- The many-to-many link dialog box allows you to: - Add a many-to-many relationship between two tables. - Create a relation table with linked columns that are derived from the two tables. - Select the Left Table, which is the first table that is linked. The Left Table has the ``one`` endpoint of the link with the new relation table. - Select the Left table Column, which is the first table’s column. The Left table Column is a primary key. - Select the Right Table, which is the second table that is linked. The Right Table has the ``one`` endpoint of the link with the new relation table. - Select the Right table Column, which is the second table’s column. The Right table Column is a primary key. Table link ---------- .. figure:: /images/erd_table_link.png :width: 70% :alt: ERD Tool - Table Link ERD Tool - Table Link The table link shows the relationship between tables: - The single-line endpoint of the link shows the column that is the reference. - The three-line endpoint of the link shows the column that references. - If one of the columns that is a reference or that references is removed from the table, then the link drops. - Select the link to drag it on the canvas. Table notes ----------- To add a note to a table: 1. On the toolbar, select **Add/Edit note**. 2. In the window, enter your note. When a note is added to a table, **Note** becomes enabled on the Table node. To check or update notes, select **Note**.