YouTipSql Alias
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By using SQL, you can assign aliases to table names or column names.
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## SQL Aliases
By using SQL, you can assign aliases to table names or column names.
Basically, aliases are created to make column names more readable.
### SQL Syntax for Column Aliases
SELECT column_name AS alias_name FROM table_name;
### SQL Syntax for Table Aliases
SELECT column_name(s) FROM table_name AS alias_name;
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## Demo Database
In this tutorial, we will use the sample database.
Here is the data selected from the "Websites" table:
mysql> SELECT * FROM Websites;+----+---------------+---------------------------+-------+---------+| id | name | url | alexa | country |+----+---------------+---------------------------+-------+---------+| 1 | Google | https://www.google.cm/ | 1 | USA || 2 | Taobao | https://www.taobao.com/ | 13 | CN || 3 | | 5000 | USA || 4 | Weibo | http://weibo.com/ | 20 | CN || 5 | Facebook | https://www.facebook.com/ | 3 | USA || 7 | Stack Overflow | http://stackoverflow.com/ | 0 | IND |+----+---------------+---------------------------+-------+---------+
Here is the data from the "access_log" website access log table:
mysql> SELECT * FROM access_log;+-----+---------+-------+------------+| aid | site_id | count | date |+-----+---------+-------+------------+| 1 | 1 | 45 | 2016-05-10 || 2 | 3 | 100 | 2016-05-13 || 3 | 1 | 230 | 2016-05-14 || 4 | 2 | 10 | 2016-05-14 || 5 | 5 | 205 | 2016-05-14 || 6 | 4 | 13 | 2016-05-15 || 7 | 3 | 220 | 2016-05-15 || 8 | 5 | 545 | 2016-05-16 || 9 | 3 | 201 | 2016-05-17 |+-----+---------+-------+------------+9 rows in set (0.00 sec)
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## Column Alias Examples
The following SQL statement specifies two aliases: one for the name column and one for the country column. **Tip:** If a column name contains spaces, you must use double quotes or square brackets:
## Example
SELECT name AS n, country AS c
FROM Websites;
Execution output result:
!(
In the following SQL statement, we combine three columns (url, alexa, and country) and create an alias named "site_info":
## Example
SELECT name, CONCAT(url, ', ', alexa, ', ', country) AS site_info
FROM Websites;
Execution output result:
!(
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## Table Alias Examples
The following SQL statement selects all access records for "". We use the "Websites" and "access_log" tables and assign them table aliases "w" and "a" respectively (using aliases makes the SQL shorter):
## Example
SELECT w.name, w.url, a.count, a.date
FROM Websites AS w, access_log AS a
WHERE a.site_id=w.id and w.name="";
Execution output result:
!(
The same SQL statement without aliases:
## Example
SELECT Websites.name, Websites.url, access_log.count, access_log.date
FROM Websites, access_log
WHERE Websites.id=access_log.site_id and Websites.name="";
Execution output result:
!(
Aliases are particularly useful in the following situations:
* When a query involves more than one table
* When functions are used in the query
* When column names are long or hard to read
* When you need to combine two or more columns together