The meaning of as in sql

The AS keyword in SQL is used to assign the name of an alias or subquery, thereby providing the following benefits: improving query readability and assigning a more descriptive alias. Simplify complex queries and assign aliases to subqueries. Prevent name conflicts and avoid conflicts caused by duplicate table or column names.

The meaning of AS in SQL

The AS keyword in SQL is used to assign an alias or subquery. name. An alias is an alternative name to the original name, and a subquery is a separate query nested within the main query.

Alias ​​

• is used to assign a different name to a table, column, or expression.
• Using syntax: Original name AS alias

• For example:

  <code class="sql">SELECT customer_id AS cust_id, customer_name AS cust_name
  FROM customers;</code>

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  In the above query, customer_id is aliased as cust_id, and customer_name is aliased as cust_name.

Subquery

• A subquery is a separate query nested within the main query.
• Usage syntax: (subquery) AS alias

• For example:

  <code class="sql">SELECT *
  FROM customers
  WHERE customer_id IN (SELECT customer_id FROM orders);</code>

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  In the above query, subquery (SELECT customer_id FROM orders) Finds customers with customer_id in the orders table. The result set is aliased as customer_id.

Benefits

Using the AS keyword can bring the following benefits:

• Improve query readability: Hard-to-remember names can be assigned more descriptive aliases.
• Simplify complex queries: You can make the main query easier to understand by assigning aliases to subqueries.
• Prevent name conflicts: If the table or column names are the same, you can use aliases to avoid conflicts.

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