等值连接查询

• 等值连接等价于 [INNER] JOIN 内连接, 返回两个表中联结字段相等的行，即得到的结果是两张表的交集

语法

SELECT a.<col_name_a>, b.<col_name_b> ...

FROM  <tbl_name_a> AS a, <tbl_name_b> AS b

WHERE a.col_name  = b.col_name;

示例

SELECT  studentNo, studentResult

FROM student AS s, result AS r

WHERE s.studentNo = r.studentNo

运行结果如下：

非等值连接

非等值连接与等值连接不同的是，连接条件的关系是非等量关系

语法

SELECT a.<col_name_a>, b.<col_name_b> ...

FROM  <tbl_name_a> AS a, <tbl_name_b> AS b

WHERE where_condition;

示例

SELECT  studentNo, studentResult

FROM student AS s, result AS r

WHERE r.studentResult BETWEEN 90 AND 80;

运行结果如下：