FROMclause by commas, and that is implicitly a cross product of those tables.
JOINoperators. There are a few different types, and they are listed below:
INNER JOINon condition
NATURAL JOINoperator equates all columns with the same name in the tables that are being joined. It requires the values in the columns to be the same in order to keep the elements in the cross product. This type of join also eliminates any duplicate columns that are created.
INNER JOIN USING(attrs)
INNER JOIN, however this type of join takes a special clause called
USINGand listing attributes. This is sort of like the
NATURAL JOIN, except you specifically state the attributes that you want to be equated.
LEFT OUTER JOIN, the
RIGHT OUTER JOIN, and the
FULL OUTER JOIN. These joins combine elements similar to the
INNER JOIN, except when elements don't match the
INNER JOINcondition, they're still added to the result and padded with
OUTER JOIN, for it is very difficult to express without the