There are two types of aliases that are used most frequently in SQL commands: a column alias and a table alias.
There are a variety of reasons that alias may be helpful when querying SQL commands.
- alias in a long query can make your query easier to read and understand
- alias table is use when using a same table in one query
- alias column is to identify the column naming when used together with aggregate functions, then the column is easily understood
In this instance this page describes a table alias. Multiple member files were quite common in IBM midrange computers from the S/36, S38, to the AS/400. SQL was not equipped to deal with these type file objects until OS/400 R430, which added support of an SQL alias statement. Create an alias for each member that must be accessed, then reference the alias from the application. The alias is a persistent object -- it must be created only once. The member referenced in the CREATE ALIAS does not have to exist when the ALIAS is created. Any SQL tool, such as OS/400 or i5/OS interactive SQL (STRSQL) or Operations Navigator, can be used to create the alias, for example:
- CREATE ALIAS MYLIB.FILE1MBR1 FOR MYLIB.MYFILE(MBR1)
- CREATE ALIAS MYLIB.FILE1MBR2 FOR MYLIB.MYFILE(MBR2)
The application then specifies the alias, MYLIB.FILE1MBR1 or MYLIB.FILE1MBR2, depending on which member it wants to access.
- runsql stm('CREATE ALIAS mblib/adaterpmbr FOR mblib/qrpglesrc(adaterp)')
- runsql stm('select * from mblib/adaterpmbr')