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Practice

Aliases in Joins

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

Aliases 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 make query results easier to read and are especially helpful in dashboards and reports.


Why are aliases useful in joins?​

You should use aliases when:

  • When joining multiple tables with similar column names
  • When performing self joins (you must alias the same table twice)
  • When writing queries that need to stay readabl for analysis, reporting, or BI dashboards

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