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# PostgreSQL Alias We can use SQL to rename the name of a table or a field. This name is called the alias of the table or field. Creating aliases is to make the table name or column name more readable. In SQL, **AS** is used to create aliases. ### Syntax Table alias syntax: SELECT column1, column2.... FROM table_name AS alias_name WHERE ; Column alias syntax: SELECT column_name AS alias_name FROM table_name WHERE ; ### Example Create the COMPANY table ((https://static.jyshare.com/download/company.sql) ), with the following data: tutorialdb# select * from COMPANY; id | name | age | address | salary ----+-------+-----+-----------+-------- 1 | Paul | 32 | California| 20000 2 | Allen | 25 | Texas | 15000 3 | Teddy | 23 | Norway | 20000 4 | Mark | 25 | Rich-Mond | 65000 5 | David | 27 | Texas | 85000 6 | Kim | 22 | South-Hall| 45000 7 | James | 24 | Houston | 10000(7 rows) Create the DEPARTMENT table ((https://static.jyshare.com/download/department.sql) ), with the following data: tutorialdb=# SELECT * from DEPARTMENT; id | dept | emp_id ----+-------------+-------- 1 | IT Billing | 1 2 | Engineering | 2 3 | Finance | 7 4 | Engineering | 3 5 | Finance | 4 6 | Engineering | 5 7 | Finance | 6(7 rows) Now, let's use C and D as aliases for the COMPANY and DEPARTMENT tables, respectively: tutorialdb=# SELECT C.ID, C.NAME, C.AGE, D.DEPT FROM COMPANY AS C, DEPARTMENT AS D WHERE C.ID = D.EMP_ID; The result will be: id | name | age | dept ----+-------+-----+------------ 1 | Paul | 32 | IT Billing 2 | Allen | 25 | Engineering 7 | James | 24 | Finance 3 | Teddy | 23 | Engineering 4 | Mark | 25 | Finance 5 | David | 27 | Engineering 6 | Kim | 22 | Finance(7 rows) Next, let's use COMPANY_ID for the ID column and COMPANY_NAME for the NAME column to demonstrate column aliases: tutorialdb=# SELECT C.ID AS COMPANY_ID, C.NAME AS COMPANY_NAME, C.AGE, D.DEPT FROM COMPANY AS C, DEPARTMENT AS D WHERE C.ID = D.EMP_ID; The result will be: company_id | company_name | age | dept ------------+--------------+-----+------------ 1 | Paul | 32 | IT Billing 2 | Allen | 25 | Engineering 7 | James | 24 | Finance 3 | Teddy | 23 | Engineering 4 | Mark | 25 | Finance 5 | David | 27 | Engineering 6 | Kim | 22 | Finance(7 rows)