
SQL SELECT AS – Column and Table Aliases in SQL
SQL SELECT AS
SQL AS
is a powerful tool that allows developers to assign temporary names to columns or tables. This feature helps improve query readability, enhances presentation, and makes result sets more understandable without permanently altering the database schema.
By using AS
, you can label columns and tables in a way that makes sense for specific queries, making it easier to analyze and interpret the data.
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Syntax of SQL SELECT AS
SELECT Column_Name1 AS New_Column_Name, Column_Name2 AS New_Column_Name FROM Table_Name;
- Column_Name: The original column name from the table.
- New_Column_Name: A temporary alias for that column.
- Table_Name: The name of the table containing the columns.
Aliases only exist for the duration of the query execution and do not modify the original database structure.
Example 1: Assigning Temporary Column Names
Consider a table named purchases with the following data:
Order_Date | Buyer | Item | Quantity |
---|---|---|---|
05-01-2022 | Rahul | Smartphone | 3 |
18-03-2022 | Simran | Laptop | 1 |
30-06-2023 | Aakash | Headphones | 5 |
Now, if we want to rename Order_Date
as Purchase_Date
and Buyer
as Customer
, we use the following query:
SELECT Order_Date AS 'Purchase_Date', Buyer AS 'Customer', Item, Quantity FROM purchases;
Result:
Purchase_Date | Customer | Item | Quantity |
---|---|---|---|
05-01-2022 | Rahul | Smartphone | 3 |
18-03-2022 | Simran | Laptop | 1 |
30-06-2023 | Aakash | Headphones | 5 |
As seen above, the original column names remain unchanged in the database, but for this query, we have customized their appearance.
Example 2: Using SQL AS with Aggregate Functions
Let’s consider another table named students with the following data:
Roll_No | Name | Gender | Mobile | City | Age | Marks |
---|---|---|---|---|---|---|
1 | Aman Joshi | Male | 9123456789 | Delhi | 21 | 85 |
2 | Priya Mehta | Female | 8765432109 | Mumbai | 22 | 90 |
3 | Rahul Verma | Male | 9988776655 | Kolkata | 23 | 88 |
4 | Shruti Shah | Female | 9876543210 | Chennai | 24 | 92 |
5 | Kabir Rao | Male | 9654321098 | Jaipur | 20 | 89 |
Query 1: Calculate the Average Marks
SELECT Name AS Student, AVG(Marks) AS Average_Marks FROM students;
Result:
Student | Average_Marks |
---|---|
Aman Joshi | 88.80 |
(Note: The average is calculated for all students, but SQL only returns one row since there is no GROUP BY
clause.)
Query 2: Retrieve Roll Numbers and Mobile Numbers with Custom Labels
SELECT Roll_No AS 'Student_ID', Mobile AS 'Contact' FROM students;
Result:
Student_ID | Contact |
---|---|
1 | 9123456789 |
2 | 8765432109 |
3 | 9988776655 |
4 | 9876543210 |
5 | 9654321098 |
Query 3: Combine Multiple Columns Using CONCAT()
If we want to merge the student’s mobile number and city into one column named Student_Info
, we can use CONCAT()
:
SELECT Roll_No AS 'Student_ID', CONCAT(Mobile, ', ', City) AS Student_Info FROM students;
Result:
Student_ID | Student_Info |
---|---|
1 | 9123456789, Delhi |
2 | 8765432109, Mumbai |
3 | 9988776655, Kolkata |
4 | 9876543210, Chennai |
5 | 9654321098, Jaipur |
Example 3: Assigning a Temporary Name to a Table
SQL also allows us to create table aliases for easier reference.
Consider the students table from the previous example. If we want to retrieve details for a specific student (Roll No 3) but use a shorter alias for the table, we can do this:
SELECT s.Roll_No, s.Name, s.Gender, s.Mobile, s.City FROM students AS s WHERE s.Roll_No = 3;
Here, s
is the temporary alias assigned to the students
table, making it easier to reference columns.
Result:
Roll_No | Name | Gender | Mobile | City |
---|---|---|---|---|
3 | Rahul Verma | Male | 9988776655 | Kolkata |
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Conclusion
The SQL AS
statement is an essential tool for enhancing query readability. Whether renaming columns for presentation purposes, using aliases for aggregate functions, or simplifying table references, AS
makes SQL queries more intuitive and structured.
Using aliases effectively can improve the clarity of reports, ease query maintenance, and enhance collaboration among developers and analysts. Next time you run an SQL query, try implementing aliases for better organization and interpretation!
For more database-related tutorials and SQL tips, stay connected with UpdateGadh.
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