sql / beginner
Snippet
Defining Unique Identifiers with Primary Keys
A PRIMARY KEY constraint uniquely identifies each record in a database table. Primary keys must contain unique values and cannot contain NULL values.
snippet.sql
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CREATE TABLE users (user_id INT NOT NULL,username VARCHAR(50) NOT NULL,CONSTRAINT pk_users PRIMARY KEY (user_id));
Breakdown
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CREATE TABLE users (
Starts the creation of a new table named users.
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user_id INT NOT NULL,
Defines an integer column that cannot store NULL values.
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username VARCHAR(50) NOT NULL,
Defines a variable-length character column up to 50 characters.
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CONSTRAINT pk_users PRIMARY KEY (user_id)
Enforces unique values and non-nullability for user_id as the primary key.
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);
Closes the table creation statement.