Question

我有两张桌子[basic]＆amp; [info]都有一个主键email_id。现在我想从basic表中检索信息，但where子句应该具有来自两个表的搜索条件

示例：

SELECT DISTINCT 
    basic.f_name, 
    basic.l_name 
FROM 
    basic 
CROSS JOIN 
    info 
WHERE 
    (basic.email_id = basic.email_id) 
    AND (basic.caste LIKE '%' + @caste + '%') 
    AND (info.diet =  @diet )

（此查询用asp编写，用于gridview但不起作用）

Answer 1

SELECT basic.f_name, basic.l_name 
FROM basic INNER JOIN info ON basic.email_id = info.email_id 
WHERE (basic.caste LIKE '%' + @caste + '%') AND (info.diet = @diet )

Answer 2

当您进行内部联接时，实际上您正在使用带有where子句的交叉联接。在内部联接中，所有数据被组合（笛卡尔积），然后使用where子句进行过滤。因此，我认为使用内部联接可以使代码更清晰。

SELECT DISTINCT basic.f_name, basic.l_name 
FROM basic 
CROSS JOIN info 
WHERE (basic.email_id = basic.email_id)

相当于

SELECT basic.f_name, basic.l_name 
FROM basic INNER JOIN info ON basic.email_id = info.email_id

我认为这可以解决您的问题。

Answer 3

使用INNER JOIN

SELECT DISTINCT 
    basic.f_name, 
    basic.l_name 
FROM 
    basic as basic
INNER JOIN 
    info as info 
    ON basic.email_id = info.email_id
WHERE 
    (basic.caste LIKE '%' + @caste + '%') 
    AND (info.diet =  @diet )

如何使用2个不同表中的where子句检索数据

3 个答案: