mysql - 这两个 SQL 语句有何不同？

Question

1:

$query = mysql_query("
SELECT table_one.row 
FROM table_one 
INNER JOIN table_two 
ON table_two.row = $id");

2:

$query = mysql_query("
SELECT table_one.row 
FROM table_one, table_two 
WHERE table_two.row = $id");

这只是同一事物的两种写法吗？

Answer 1

他们都取得了相同的结果，但采用了不同的方法。尽管您滥用了 ON 子句。

我会建议这样的事情:

$query = mysql_query("
SELECT table_one.row 
FROM table_one 
INNER JOIN table_two 
ON table_one.id = table_two.id
WHERE table_two.row = $id");

引自 mysql 站点:

The conditional_expr used with ON is any conditional expression of the form that can be used in a WHERE clause. Generally, you should use the ON clause for conditions that specify how to join tables, and the WHERE clause to restrict which rows you want in the result set.