a join is a relationship of equality between one or several bases.
No, I do not know what you mean but this is not "between several bases".
a natural join is equivalent to time, a performance and logical of a "WHERE table1.value = table2.value".
Basically yes
It is also equivalent to a
Code:
INNER JOIN Table2
ON table1.value = table2.value
An outer join is equivalent to a natural join with the exception that it includes all entries in the table specified after FROM for a left outer join and right outer join after a right outer join.
No, an outer join is equivalent to an inner join. You can have a
Code:
FROM Table1
LEFT OUTER JOIN Table2
ON Table1.Field1 = Table2.Field2
It is used to verify equal while in the selection encompassing all entries compared with the field is NULL.
Not compared with the field has no match in the other table.
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