Defining Primary Key 1 column as Primary key

sweethoney (54)in #pk • 9 months ago

Yes, the provided SQL syntax can be used to create a table for staff members in a college with the Email column defined as the primary key. The syntax you provided is correct. Here's a breakdown of the SQL statement:

CREATE TABLE Staff: This command creates a new table named Staff.
Email VARCHAR(200) NOT NULL: This defines a column named Email with a data type of VARCHAR and a maximum length of 200 characters. The NOT NULL constraint ensures that the Email field cannot contain NULL values.
Name VARCHAR(255) NOT NULL: This defines a column named Name with a data type of VARCHAR and a maximum length of 255 characters. The NOT NULL constraint ensures that the Name field cannot contain NULL values.
CONSTRAINT PK_Email PRIMARY KEY (Email): This adds a constraint to the table, naming it PK_Email, and sets the Email column as the primary key for the table. The primary key constraint ensures that each value in the Email column is unique and not null.

The complete SQL syntax is:

CREATE TABLE Staff (
    Email VARCHAR(200) NOT NULL,
    Name VARCHAR(255) NOT NULL,
    CONSTRAINT PK_Email PRIMARY KEY (Email)
);

This syntax will successfully create the Staff table with Email as the primary key.

9 months ago in #pk by sweethoney (54)

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sweethoney (54) 9 months ago

Certainly! Here is another example of creating a table with a different context, where one column is constrained as the primary key:

Suppose we are creating a table for a library system to keep track of books. We will use the ISBN (International Standard Book Number) as the primary key, as it uniquely identifies each book.

The SQL syntax would be as follows:

CREATE TABLE Books (
    ISBN VARCHAR(13) NOT NULL,
    Title VARCHAR(255) NOT NULL,
    Author VARCHAR(255) NOT NULL,
    PublicationYear INT NOT NULL,
    CONSTRAINT PK_ISBN PRIMARY KEY (ISBN)
);

Explanation:

CREATE TABLE Books: This command creates a new table named Books.
ISBN VARCHAR(13) NOT NULL: This defines a column named ISBN with a data type of VARCHAR and a maximum length of 13 characters. The NOT NULL constraint ensures that the ISBN field cannot contain NULL values.
Title VARCHAR(255) NOT NULL: This defines a column named Title with a data type of VARCHAR and a maximum length of 255 characters. The NOT NULL constraint ensures that the Title field cannot contain NULL values.
Author VARCHAR(255) NOT NULL: This defines a column named Author with a data type of VARCHAR and a maximum length of 255 characters. The NOT NULL constraint ensures that the Author field cannot contain NULL values.
PublicationYear INT NOT NULL: This defines a column named PublicationYear with a data type of INT (integer). The NOT NULL constraint ensures that the PublicationYear field cannot contain NULL values.
CONSTRAINT PK_ISBN PRIMARY KEY (ISBN): This adds a constraint to the table, naming it PK_ISBN, and sets the ISBN column as the primary key for the table. The primary key constraint ensures that each value in the ISBN column is unique and not null.

This syntax will successfully create the Books table with ISBN as the primary key.

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