Drizzle MSSQL Schema Patterns

MSSQL-specific schema definition guide for Drizzle ORM. Contains 10 rules covering data types, constraints, and patterns unique to Microsoft SQL Server.

When to Apply

Reference these guidelines when:

• •Defining schemas for Microsoft SQL Server databases
• •Choosing appropriate MSSQL data types (varchar vs nvarchar, datetime vs datetime2)
• •Working with MSSQL-specific features (uniqueidentifier, identity columns)
• •Avoiding MSSQL limitations (unique constraints on max-length types)
• •Setting up connection pools with the mssql driver

Rule Categories by Priority

Quick Reference

1. Data Types (CRITICAL-HIGH)

• •types-string - varchar, nvarchar, char, nchar, text, ntext with length considerations
• •types-integer - int, bigint, smallint, tinyint with modes
• •types-datetime - datetime, datetime2, date, time, datetimeoffset
• •types-numeric - decimal, numeric, real, float
• •types-boolean - bit type for true/false values
• •types-uuid - uniqueidentifier for GUIDs
• •types-binary - binary, varbinary for byte data

2. Constraints (CRITICAL-HIGH)

• •constraint-unique-limitations - Cannot use unique on text/ntext/varchar(max)/nvarchar(max)
• •constraint-identity-columns - Auto-incrementing primary keys

3. Patterns (HIGH)

• •pattern-connection-pool - Proper connection pool setup with async initialization

MSSQL-Specific Imports

import {
  mssqlTable,
  int, bigint, smallint, tinyint,
  varchar, nvarchar, char, nchar, text, ntext,
  datetime, datetime2, date, time, datetimeoffset,
  decimal, numeric, real, float,
  bit,
  uniqueIdentifier,
  binary, varbinary,
  primaryKey, foreignKey, unique, index, uniqueIndex, check,
} from 'drizzle-orm/mssql-core';

Critical MSSQL Limitations

Cannot create unique constraints or indexes on:

• •text
• •ntext
• •varchar(max) / varchar({ length: 'max' })
• •nvarchar(max) / nvarchar({ length: 'max' })

Always use bounded length strings for columns requiring uniqueness.

How to Use

Read individual rule files for detailed explanations and code examples:

rules/types-string.md
rules/constraint-unique-limitations.md
rules/pattern-connection-pool.md

Full Compiled Document

For the complete guide with all rules expanded: AGENTS.md