Why does this SQL code give error 1066 (Not unique table/alias: 'customer')?

Why does the MySQL query below give error 1066 (Not unique table/alias: 'customer')?

SELECT customer.id, customer.firstName, account.id
FRO开发者_运维知识库M customer, account
INNER JOIN customer
ON customer.id = account.customerId 
ORDER BY customer.id

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You have listed the table customer twice in your FROM statement. Here's the fixed version:

SELECT customer.id, customer.firstName, account.id
FROM account
INNER JOIN customer
ON customer.id = account.customerId
ORDER BY customer.id