SQL SERVER 2012 Chapter Fourth joins the Joinのouter join, fully connects full joins, crosses Cross joins

Select <select list> from <the table want to being the "left" table> <left| right> [OUTER] JOIN <table you want to be the ' right ' table> on <join condition>

The table before the join can be seen as the left table, and then the table is the right table.

An external connection is essentially a containment. The records that are explicitly included depend on which side of the connection is used. The left OUTER join contains information from the table on the right side, and it comes from the side.

The commonly used usage is to find which records in one table do not match the records in another table .

For null values, two null is not equal. Null means "I don't know", and null and null comparisons are meaningless.

Full join returns all the table data. Is independent of the left and right order of the table.

Cross JOIN produces a Cartesian product. This multiplication is generally used to generate large amounts of test data.

SQL SERVER 2012 Chapter Fourth joins the Joinのouter join, fully connects full joins, crosses Cross joins