SQL alias
By using SQL, you can specify aliases for table names or column names.
SQL Aliases
Using SQL, you can specify aliases for table names or column names.
Basically, aliases are created to make column names more readable.
SQL alias syntax for columns
FROM table_name;
SQL alias syntax for table
FROM table_name AS alias_name;
Demo Database
In this tutorial, we will use the php sample database.
The following is the data selected from the "Websites" table:
| id | name | url --------+-------+---------+
| 1 | Google | https://www.google.cm/ | 1 | USA |
| 2 | Taobao | https://www.taobao.com/ | 13 | CN |
| 3 | php Chinese website | http://www.php.cn/ | 4689 | CN |
| 4 | Weibo | http://weibo.com/ | 20 | CN |
| 5 | Facebook | https://www.facebook.com/ | 3 | USA |
| 7 | stackoverflow | http://stackoverflow.com/ | 0 | IND |
+----+---------------+----------- ----------------+-------+---------+
The following is the data of the "access_log" website access record table:
+-----+--------- +-------+------------+
| 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 | 201 6-05 -16 |
| 9 | 3 | 201 | 2016-05-17 |
+-----+----------+------+--- ---------+
9 rows in set (0.00 sec)
Alias instance of column
The following SQL statement specifies two Alias, one is the alias of the name column, and the other is the alias of the country column. Tip: If the column name contains spaces, double quotes or square brackets are required:
Example
FROM Websites ;
Execution output result:
In the following SQL statement, we put four columns (name, url, alexa and country) Combined together and create an alias called "site_info":
Instance
FROM Websites;
Execution output result:
Table alias example
The following SQL statement selects the accessed records of "php Chinese website". We use the "Websites" and "access_log" tables and give them table aliases "w" and "a" respectively (using aliases makes the SQL shorter):
Example
FROM Websites AS w, access_log AS a
WHERE a.site_id=w.id and w.name="php中文网";
Execution output result:
The same SQL statement without alias:
Example
FROM Websites, access_log
WHERE Websites.id=access_log.site_id and Websites.name="php中文网";
Execution output result:
In the following situations, using aliases is useful:
In More than one table is involved in the query
A function is used in the query
The column name is very long or poorly readable
Need to combine two or more columns
