Last updated: 2026-02-12
Table Designer
Create and modify database tables with a visual interface. Table Designer lets you define columns, set data types, configure primary keys and identity columns, and preview the generated DDL scripts before executing.
Creating a New Table
Use Table Designer to create tables without writing SQL manually.
Opening Table Designer
- Click More in the toolbar
- Select Table Designer
- Or press
Cmd+Shift+T(macOS) /Ctrl+Shift+T(Windows/Linux)

Setting Table Properties
- Select the Database where the table will be created
- Optionally select a Schema (defaults to
dbofor SQL Server) - Enter the Table Name (e.g.,
Products,Customers)
Adding Columns
- Click Add Column or press the
+button - Enter the column name
- Select a data type from the dropdown
- Configure column properties (nullable, primary key, etc.)
- Repeat for each column
Column Properties
Each column has several configurable properties:

Column Name
Enter a descriptive name for the column. Follow your database naming conventions (e.g., ProductID, product_id, productId).
Data Type
Select the appropriate data type from the dropdown. Common types include:
| Category | SQL Server | PostgreSQL |
|---|---|---|
| Integer | int, bigint, smallint | integer, bigint, smallint |
| Decimal | decimal(p,s), money | numeric(p,s), decimal |
| Text | varchar(n), nvarchar(n) | varchar(n), text |
| Date/Time | datetime, date, time | timestamp, date, time |
| Boolean | bit | boolean |
| Binary | varbinary(n) | bytea |
Length/Precision
For certain data types, specify:
- Length - Maximum characters for
varchar(n) - Precision - Total digits for
decimal(p,s) - Scale - Decimal places for
decimal(p,s)
Nullable
Check Allow NULL to permit NULL values. Uncheck to require a value (NOT NULL constraint).
Primary Key
Check Primary Key to include this column in the table's primary key:
- Primary key columns are automatically NOT NULL
- Select multiple columns for a composite primary key
- Primary keys create a clustered index by default (SQL Server)
Identity / Auto-Increment
Enable Identity for auto-incrementing numeric columns:
SQL Server
- Check the Identity checkbox
- Seed - Starting value (default: 1)
- Increment - Step value (default: 1)
PostgreSQL
- Select
SERIALorBIGSERIALdata type - Or use
GENERATED ALWAYS AS IDENTITY
Default Value
Enter a default value expression:
0- Numeric default''- Empty stringGETDATE()- Current date/time (SQL Server)NOW()- Current date/time (PostgreSQL)NEWID()- New GUID (SQL Server)
Modifying Existing Tables
Open existing tables in Table Designer to make changes.
Opening in Alter Mode
- Find the table in Object Explorer
- Right-click the table
- Select Design Table

Adding New Columns
- Click Add Column to append a new column
- New columns are added at the end of the table
- Consider adding a default value if the table has existing data
Modifying Existing Columns
You can modify some properties of existing columns:
| Change | Allowed? | Notes |
|---|---|---|
| Increase varchar length | Yes | Data preserved |
| Decrease varchar length | Limited | May truncate data |
| Change data type | Limited | Must be compatible |
| Add NOT NULL | Conditional | No existing NULLs |
| Remove NOT NULL | Yes | Always allowed |
| Add default value | Yes | Always allowed |
Deleting Columns
- Select the column to delete
- Click the Delete button or press
Delete - The column is marked for deletion (shown with strikethrough)
- Column is removed when you save the changes
Saving Changes
Table Designer generates DDL scripts for your changes.
Preview Script
- Click Preview Script to see the generated SQL
- Review the CREATE TABLE or ALTER TABLE statements
- Copy the script if needed for version control
Reset Changes
- Click Reset to discard all pending (unsaved) edits
- In Design (alter) mode the columns revert to the table's last-saved state; in New Table mode the draft columns are cleared
- Reset is enabled only while there are unsaved changes
Execute Script
- Click Apply to execute the script
- Table Designer creates/modifies the table
- The Object Explorer refreshes to show changes
- Any open Table Explorer for the same table refreshes its cached schema too — so a newly-added primary key re-enables Edit Mode without restarting the app
Dirty State Indicator
- An asterisk (*) in the tab title indicates unsaved changes
- Modified columns are highlighted
- Added columns show an "add" indicator
- Deleted columns show a strikethrough
Best Practices
Naming Conventions
- Use consistent naming (PascalCase, snake_case, or camelCase)
- Avoid reserved words as column names
- Use singular nouns for table names (Product not Products)
Primary Keys
- Every table should have a primary key
- Consider using identity columns for surrogate keys
- Use meaningful columns for natural keys when appropriate
Data Types
- Choose the smallest appropriate data type
- Use
varcharinstead ofcharfor variable-length strings - Use
decimalfor monetary values (notfloat)
Frequently asked questions
How do I create a new table in Jam SQL Studio?
Open Table Designer from the toolbar (More → Table Designer), enter a table name, add columns with their data types and properties, then click Save to generate and execute the CREATE TABLE script.
Can I modify an existing table with Table Designer?
Yes, right-click any table in the Object Explorer and select 'Design Table' to open it in Table Designer. You can add new columns, modify properties of existing columns (with some limitations), and preview the ALTER TABLE script before executing.
How do I set a primary key in Table Designer?
Click the Primary Key checkbox next to any column to mark it as part of the primary key. You can select multiple columns to create a composite primary key. Primary key columns are automatically marked as NOT NULL.
How do I create an auto-increment column?
For SQL Server, enable the Identity checkbox and optionally set the seed and increment values. For PostgreSQL, use the SERIAL or BIGSERIAL data type. Identity columns are automatically configured with starting values.
Can I preview the DDL script before executing?
Yes, click the 'Preview Script' button to see the generated CREATE TABLE or ALTER TABLE statement. You can review, copy, or modify the script before executing it against the database.
Ready to Design Tables?
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