SQL Server non-join statement differs from with join statement

1. Connect two tables query select * from TABLE1,TABLE2//2. Connecting two table queries select * FROM table1 join table2 on Table1.id=table2.id

1. The result of the first connection query is a Cartesian product: That is, the row count of table 1 multiplied by the number of rows in table 2 (each record in table one will be combined with each record in table two)
Such as:

Table One Table II

1 A

2 b

3 C

The result after the build is: 3x3 Strip records

1 A

1 b

1 c

2 A

2 b

2 C

3 A

3 b

3 C

2. The result of the second connection query is a record that conforms to table1.id=table2.d_id, and the statement after on is equivalent to a filter condition.

Table 2

ID e_name d_id D_name

1 a 1 Z

1 B 2 x

2 C

3d

The resulting query result is a record with an ID equal to d_id

ID e_name d_id D_name

1 a 1 Z

1 B 1 Z

2 C 2 x

SQL Server non-join statement differs from with join statement