SQL SERVER 2012 Chapter Fourth connecting JOIN statements early syntax structure & Union Union

1/early grammatical structure of the internal connection INNER join

SELECT * from Person.person JOIN humanresources.employee on Person.Person.ID = HumanResources.Employee.ID

Equivalent to an earlier version of the old

SELECT * from Person.person,humanresources.employee WHERE Person.Person.ID = HumanResources.Employee.ID

2/early syntax structure for external connections

SELECT * from Sales left JOIN Product on sales.id = product.id

Equivalent to

SELECT * from Sales,product WHERE sales.id *= product.id

3/early grammatical structure of cross-joins

SELECT * from vendors cross JOIN Address

Equivalent to

SELECT * from Vendors,address

Union Union

1, the SELECT list has the same number of columns.
2. The returned result set header is obtained from the first query.
3. The type of the corresponding column must be implicitly convertible. Parts that are out of length are ignored.
4. The Union default return option is distinct, not all. Use UNION All if you want it all.

SQL SERVER 2012 Chapter Fourth connecting JOIN statements early syntax structure & Union Union