What does as in SQL statements mean ?, SQL statement

What does as in SQL statements mean ?, SQL statement

As is generally used in two places. When one is a query, it is used to re-specify the name of the returned column (column ).
For example, a table has a column named id, and our query is
Select id from table1. but if you don't want to call the id, you can rename it, such as systemID.
Select id as systemId from table1;

Another usage is that when creating table or procedure, as is a keyword.
For example
Create table test as select * from table1
At this time, a table test is created, which completely copies all the data in table 1.

Create procdure name as (is)
Begin
End;
For details, refer to how to create procedure. At this time, as and is can be exchanged.