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Practice

Aliases in Joins

As SQL queries grow more complex, using aliases helps improve readability and structure.

Aliases allow you to assign temporary, clear names to tables and columns, making multi-join queries easier to follow.


Table Aliases​

Use the AS keyword (or omit it) to give a meaningful alias to a table:

Table alias with AS
SELECT students.name, enrollments.class_id
FROM students AS students
JOIN enrollments AS enrollments
ON students.student_id = enrollments.student_id;

You can also omit AS:

Table alias without AS
FROM students students
JOIN enrollments enrollments ...

This avoids repeating long table names and is useful when joining multiple tables.


Column Aliases​

Use AS to rename output columns for clarity:

Column alias
SELECT 
  students.name AS student_name, 
  enrollments.class_id AS course
FROM students students
JOIN enrollments enrollments
ON students.student_id = enrollments.student_id;

Output​

student_namecourse
AlexA1
SaraA2

Column aliases help make query results easier to read and are especially helpful for dashboards or reports.


When to Use Aliases​

You should use aliases when:

  • Joining multiple tables with similar column names
  • Performing self joins (you must alias the same table twice)
  • Writing readable queries for analysis, reporting, or BI dashboards

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