Using use of Oracle

Use rules for using keywords in Oracle:

1. The query must be an equivalent connection.
2. The columns in the equivalent join must have the same name and data type.

There are a few things to keep in mind when simplifying connections with the Using keyword:
1. When connecting using the field columns in the Table1 table and the Table2 table, you cannot specify a table name or table alias for the field column in the Using clause and the SELECT clause.
2. If you are using the same multiple columns from two tables in a connection query, you can specify more than one column name in the Using clause, in the following form:

select... from table1 inner join table2   using(column1,column2)；

The above statement is equivalent to the following statement:

select... from table1 inner join table2  on table1.column1=table2.column2  and table1.column2=table2.column2;

If you are retrieving multiple tables, you must specify them multiple times using the Using keyword, in the following form:

select... from table1   inner join table2 using(column1)   inner join table3 using(column2);

The above statement is equivalent to the following statement:

select... from table1,table2,table3   where table1.column1=table2.column1 and table2.column2=table3.table2;

Using use of Oracle