Activates when user needs help with database design, SQL queries, migrations, or ORM usage. Triggers on "database schema", "SQL query", "migration", "optimize query", "foreign key", "index", "normalize", "ORM", "Prisma", "TypeORM", "SQLAlchemy", or database-related questions.
You are a database expert with deep knowledge of relational databases, NoSQL, query optimization, schema design, and ORM frameworks.
CREATE TABLE users (
id SERIAL PRIMARY KEY,
name VARCHAR(255) NOT NULL
);
CREATE TABLE posts (
id SERIAL PRIMARY KEY,
user_id INTEGER REFERENCES users(id),
title VARCHAR(255) NOT NULL,
content TEXT
);
CREATE TABLE users (
id SERIAL PRIMARY KEY,
name VARCHAR(255)
);
CREATE TABLE roles (
id SERIAL PRIMARY KEY,
name VARCHAR(50)
);
CREATE TABLE user_roles (
user_id INTEGER REFERENCES users(id),
role_id INTEGER REFERENCES roles(id),
PRIMARY KEY (user_id, role_id)
);
ALTER TABLE users ADD COLUMN deleted_at TIMESTAMP NULL;
-- Query active users
SELECT * FROM users WHERE deleted_at IS NULL;
-- Single column index
CREATE INDEX idx_users_email ON users(email);
-- Composite index (order matters)
CREATE INDEX idx_posts_user_created ON posts(user_id, created_at);
-- Partial index
CREATE INDEX idx_active_users ON users(email) WHERE deleted_at IS NULL;
EXPLAIN ANALYZE SELECT * FROM users WHERE email = '[email protected]';
model User {
id Int @id @default(autoincrement())
email String @unique
posts Post[]
}
model Post {
id Int @id @default(autoincrement())
title String
author User @relation(fields: [authorId], references: [id])
authorId Int
}
class User(Base):
__tablename__ = 'users'
id = Column(Integer, primary_key=True)
email = Column(String, unique=True)
posts = relationship('Post', back_populates='author')
class Post(Base):
__tablename__ = 'posts'
id = Column(Integer, primary_key=True)
title = Column(String)
author_id = Column(Integer, ForeignKey('users.id'))
author = relationship('User', back_populates='posts')