在我的MySQL中，使用单词JOIN或使用：table1.id = table2.id有什么区别？

Question

In my MySQL what is the difference between using the word JOIN or using: table1.id=table2.id

Table 1
id  name
1   John Lennon

Table 2
id  position
1   Singer

//What is the difference then calling JOIN?

Select name, position
From Table1, Table2
Where Table1.id=Table2.id;

Answer 1

If this case, there's no difference. But the joins can also be: INNER, OUTER (left outer, right outer, full outer joins), LEFT, RIGHT.

Answer 2

There is none as long as there are only two tables. When there are more, you might get different JOIN order than expected, if you use comma to separate tables.

From manual :

INNER JOIN and , (comma) are semantically equivalent in the absence of a join condition: both produce a Cartesian product between the specified tables (that is, each and every row in the first table is joined to each and every row in the second table).

However, the precedence of the comma operator is less than of INNER JOIN, CROSS JOIN, LEFT JOIN, and so on. If you mix comma joins with the other join types when there is a join condition, an error of the form Unknown column 'col_name' in 'on clause' may occur. Information about dealing with this problem is given later in this section.

Answer 3

Using a JOIN is known as an "explicit join", or an ANSI join... separating your tables with a comma and then linking them in the WHERE clause is known as an "implicit join".

The ANSI join is widely considered to be the preferred syntax. It is easier to follow, less ambiguous, and more consistent when you need to start adding outer joins.

Additionally, if you use the implicit join syntax, it is easy to end up with an accidental cross join if you forget to link the tables in your WHERE clause.