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Example 1: Key join
Example 2: ON clause
join
Example 3: Natural
join
search-condition :
[ ( ] search-expression [ AND search-expression ] [ ) ]
•
The join-clause can be expressed either with or without parentheses.
•
The
clause can reference only two tables. One must be the current one,
ON
and the other can be any one table in the current join tree.
•
All join predicates must be equijoins; that is, the search_expression must
indicate that the value in column_1 equals the value in column_2. No
single-variable predicates, intracolumn comparisons, or non-equality joins
are permitted in the
•
To specify a multicolumn join, you include more than one predicate
linking the two tables, and connect them with logical AND.
•
You cannot connect join predicates with logical OR.
•
The keyword
NATURAL
columns from a single pair of tables by name.
Here is an example of how you create a join index for the key join between the
table and the
sales_order
based on the foreign key
to the primary key
sales_order
any name you want. This example names it
foreign key on which the key join relies.
CREATE JOIN INDEX ky_so_customer_join
FOR customer FULL OUTER JOIN sales_order
The next example shows how you could create a join index for the same two
tables using an
clause. You could use this syntax whether or not the foreign
ON
key existed.
CREATE JOIN INDEX customer_sales_order_join
FOR customer FULL OUTER JOIN sales_order
ON customer_id=sales_order.cust_id
To create a natural join, the joined columns must have the same name. If you
created a natural join on the tables in previous examples, you would not get the
expected results at all. Instead of joining the
column of
cust_id
sales_order
dissimilar
columns of the two tables:
id
CREATE JOIN INDEX customer_sales_order_join
FOR customer NATURAL FULL OUTER JOIN sales_order
CHAPTER 4
Adaptive Server IQ Indexes
clause.
ON
can replace the
clause, when you are pairing
ON
table. Remember that this is a key join,
customer
which relates the
ky_so_customer
of the
table. You can give the index
id
customer
ky_so_customer_join
column of
id
, the following command would join the
column of
cust_id
to identify the
to the
customer
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