ALTER TABLE in SQL

Schema changes after the fact: add, rename and drop columns.

ALTER TABLE users
ADD COLUMN timezone TEXT NOT NULL DEFAULT 'UTC';

ALTER TABLE users
RENAME COLUMN signup_date TO created_at;

ALTER TABLE users
DROP COLUMN legacy_id;

How it works

1. A new column needs a default if existing rows must stay valid.
2. Renaming keeps the data and changes only the name.
3. Dropping a column is destructive — back up first.

Keywords and builtins used here

• ADD
• ALTER
• COLUMN
• DEFAULT
• DROP
• NOT
• NULL
• RENAME
• TABLE
• TEXT
• TO

The run, in numbers

Lines

8

Characters to type

168

Tokens

28

Three-star pace

95 tpm

At the three-star pace of 95 tokens a minute, this run takes about 18 seconds.

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Step 1 of 2 in Changing a schema, step 13 of 16 in Schema & constraints.

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