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ER Diagram & Schema Studio

Local workspace
Tools
ER diagram canvas
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OVERVIEW
Click the ↗ icon beside a field to add a relationship · Select relationship lines to edit · Drag to move · Scroll to zoom
  
 
  
 
 
ER diagram guide
Model entities and foreign keys offline. Your browser holds your working projects; download JSON backups for long-term storage.
Crow's-foot notation
○│Zero or one parent — foreign key may be NULL
││Exactly one parent — foreign key required
○≺Zero or many children — ordinary foreign key
○│Zero or one child — UNIQUE foreign key
Fast diagram editing
Drag ↗ from a child field to a unique parent key to create a simple foreign key. Click ↗ to open the full composite-key editor. Use the inspector to change types, nullability, keys, indexes or cascade actions. Use Keys & foreign keys to hide descriptive fields without deleting them.
Exports and trade-offs
JSON is the lossless editable schema. SQL targets PostgreSQL, MySQL and SQLite. SVG/PNG are presentation snapshots. DBML and Mermaid support documented subsets; Mermaid export requires ASCII identifiers. Use Create junction table to model many-to-many relationships with physical join tables.
Browser storage can be removed by privacy settings or clearing site data. There is no connection to your database, no collaboration, and no execution of generated SQL.
  
 
PHYSICAL DATA MODELING
Create junction table
 
Model a many-to-many relationship using a new table. The tool creates two foreign keys, a composite primary key, and an index for the second foreign key. Select the same table twice for a self-relationship.
 
 
Both parent tables must have valid primary keys. Existing tables are not modified.
  
 
   
 
DATA INTEGRITY
New relationship
 
Connect child foreign-key columns to a parent primary key or unique index. Use Ctrl/⌘ to select multiple columns in the same table order. Composite keys must match in count and order.
 
  
 
  
Project tools
  
CODE-TO-DIAGRAM WORKFLOW
Import text schema
 
Paste a supported SQL DDL script or DBML text. Validate first; replacement is explicit and checkpoints your current working draft. Advanced SQL and DBML grammar may be unsupported.
    
Text imports retain schema structure but regenerate diagram positions and internal IDs. JSON remains the lossless editable project format.
 
Paste a schema and select Validate.
 
   
LOCAL WORKSPACE
Project library
 
Save named copies in this browser. Opening a copy makes it your working draft; later edits will not overwrite the saved copy until you choose Update. Download JSON for a backup outside this browser.
 
 
  
Restore points
Browser-only checkpoints. Export a JSON backup before clearing your browser data.
 
Schema comparison
Read-only structural differences. This is not a safe SQL migration generator; renames appear as removed and added objects.
      
 
Using ER Diagram & Schema Studio
Create tables and keys, connect relationships and review the schema before exporting. Use JSON for an editable backup and choose the supported SQL dialect or diagram format for sharing.
SQL and DBML imports support strict subsets, not arbitrary database scripts. This tool does not connect to or execute SQL on a database. New junction-table foreign keys use cascading deletes; review generated SQL. Browser project storage is best effort and separate from Database Designer.
 
Choose an editable ER schema or a database handoff
Practice: review a parent-child relationship
  1. Create fictional tables named projects and tasks with primary keys.
  2. Add a project reference to tasks and connect the relationship.
  3. Review key types and delete/update behavior, then save JSON before exporting SQL or a visual handoff.
This is an authored schema plan, not executed SQL or a verified database migration.
ER schema questions
Will importing SQL connect to or modify my database?
No. Imports accept strict supported SQL/DBML subsets for modeling. They do not connect to a server or execute scripts. Review generated SQL with the target database's requirements before using it elsewhere.
Why should I review generated junction-table foreign keys?
New junction-table foreign keys use cascading deletes in this model. Confirm that behavior fits your data-retention rules; a diagram does not establish a safe migration or permission to delete real records.
 
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