SQL migration: the ALTERs between two versions of a schema

On the left the schema as it was, on the right as it became. Below is what the editor emits to turn one into the other — real output, not an example from the docs.

Beforev1.sql

CREATE TABLE users (
    id BIGSERIAL PRIMARY KEY,
    email VARCHAR(120) NOT NULL,
    created_at TIMESTAMPTZ
);

CREATE TABLE orders (
    id BIGSERIAL PRIMARY KEY,
    user_id BIGINT NOT NULL,
    total NUMERIC(12,2) NOT NULL
);

Afterv2.sql

CREATE TABLE users (
    id BIGSERIAL PRIMARY KEY,
    email VARCHAR(255) NOT NULL,
    phone VARCHAR(120),
    created_at TIMESTAMPTZ NOT NULL,
    CONSTRAINT uq_users_email UNIQUE (email)
);

CREATE TABLE orders (
    id BIGSERIAL PRIMARY KEY,
    user_id BIGINT NOT NULL,
    total NUMERIC(12,2) NOT NULL,
    CONSTRAINT fk_orders_user FOREIGN KEY (user_id) REFERENCES users (id) ON DELETE CASCADE
);

CREATE INDEX idx_orders_user ON orders (user_id);

What comes outPostgreSQL

ALTER TABLE users ADD COLUMN phone VARCHAR(120);
ALTER TABLE users ALTER COLUMN email TYPE VARCHAR(255);
ALTER TABLE users ALTER COLUMN created_at SET NOT NULL;
ALTER TABLE users ADD CONSTRAINT uq_users_email UNIQUE (email);

CREATE INDEX idx_orders_user ON orders (user_id);

ALTER TABLE orders ADD CONSTRAINT fk_orders_user FOREIGN KEY (user_id) REFERENCES users (id) ON DELETE CASCADE;

Open the editor

The script stays in the browser: both parsing and generation run on your machine, nothing goes to a server.

The same change in different dialects

PostgreSQL	`ALTER TABLE users ALTER COLUMN email TYPE VARCHAR(255);`
MySQL / MariaDB	`ALTER TABLE users MODIFY COLUMN email VARCHAR(255) NOT NULL;`
SQL Server	`ALTER TABLE users ALTER COLUMN email NVARCHAR(255) NOT NULL;`
Oracle	`ALTER TABLE users MODIFY (email VARCHAR2(255));`

SQL migration: the ALTERs between two versions of a schema

The same change in different dialects

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