sqlserver-schema

name	sqlserver-schema
description	SQL Server DDL patterns — CREATE TABLE with proper data types, ALTER TABLE, idempotent migrations, foreign keys, computed columns, and check constraints.

SQL Server Schema Management

Use this skill for creating and modifying database schemas, writing migration scripts, and applying DDL best practices.

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CREATE TABLE — Data Type Guide

CREATE TABLE dbo.Customers (
    -- Integer IDs
    CustomerID      INT             NOT NULL IDENTITY(1,1),  -- INT (up to ~2.1B rows); use BIGINT for very large tables
    ExternalRef     BIGINT          NULL,                     -- BIGINT when interfacing with external systems

    -- Strings
    CompanyName     NVARCHAR(200)   NOT NULL,                 -- NVARCHAR for Unicode (internationalization)
    CountryCode     CHAR(2)         NOT NULL,                 -- CHAR for fixed-length strings (ISO codes, etc.)
    Notes           NVARCHAR(MAX)   NULL,                     -- MAX only when truly variable length > 4000 chars

    -- Dates and Times
    CreatedAt       DATETIME2(7)    NOT NULL DEFAULT GETUTCDATE(),  
    UpdatedAt       DATETIME2()    ,
    BirthDate                   ,                     
    AppointmentTime ()         ,                     

    
    AccountBalance  (,)     ,       

    
    IsActive        BIT               ,       

    
    PublicToken     UNIQUEIDENTIFIER   NEWSEQUENTIALID(),  

    
     PK_Customers  CLUSTERED (CustomerID),
     UQ_Customers_CompanyName  (CompanyName),
     CK_Customers_CountryCode  (LEN(CountryCode)  )
);