SQL Alias
SQL Alias are the temporary names given to table or column for the purpose of a specific SQL query.
SQL Alias name specifies to make table or column name are more readable. Alias assigning is optional not a compulsory.
You can temporary assign another name to a table or a column name for a duration of SELECT query using as alias name.
When you joining one or more table that time assign alias name of a table or a column name to make easier to read.
Alias Useful When...
- column name is big and complex assign alias name.
- use aggregate function assign alias name.
- JOIN one or more table query structure make more readable assign alias name.
- More than one columns are combined together to assign alias name.
Syntax
Look this syntax column_name AS alias_column_name and table_name alias_table_name no need AS keyword. Considering following syntax that help you to understanding Alias,
SELECT
column_name [AS alias_column_name], aggregate_function(column_name) [AS alias_name], ...
FROM table_name [ alias_table_name ];
Example Table
We have following employee_hour table that store weekday hours for each employee:
SQL> SELECT * FROM employee_hour;
NAME DAY HOURS
-------------------- ---------- ----------
Opal Kole Monday 8
Max Miller Monday 8
Beccaa Moss Monday 8
Paul Singh Monday 9
Opal Kole Tuesday 9
Max Miller Tuesday 6
Beccaa Moss Tuesday 10
Paul Singh Tuesday 8
Opal Kole Wednesday 7
Max Miller Wednesday 9
Beccaa Moss Wednesday 11
Paul Singh Wednesday 12
12 rows selected.
Example
SQL> SELECT
name AS Employee_Name, SUM(hours) AS Total_Hours
FROM employee_hour emp_hours
GROUP BY name;
EMPLOYEE_NAME TOTAL_HOURS
-------------------- -----------
Opal Kole 24
Beccaa Moss 29
Paul Singh 29
Max Miller 23