Question

我创建了这个搜索sql。但我只想搜索那些血型为a +的人，而不是khilgoan师dhaka和地区dhaka。但我的搜索结果没有显示

Select          d.user_id,
                d.firstname,
                d.`blood_group`,
                a.`city_thana`,
                a.`division`,
                a.`district` 
From            donar d 
natural join    addrsess a
where           `blood_group` = 'A+' 
and             a.`city_thana` = 'Khilgoan' 
and             a.`division` = 'Dhaka' 
and             a.`district` = 'Dhaka'

Answer 1

由于无法查看表格的投放，natural join可能会弄乱查询，因为所有具有相同名称的列都将加入

Answer 2

只有当您确定两个表都具有相同名称的公共字段时，才能或应该执行Natural Join，否则请明确执行INNER JOIN。尝试使用显式连接修改您的查询，例如

Select          d.user_id,
                d.firstname,
                d.`blood_group`,
                a.`city_thana`,
                a.`division`,
                a.`district` 
From            donar d 
INNER JOIN      addrsess a ON d.user_id = a.user_id  (may be other column)
where           d.`blood_group` = 'A+' 
and             a.`city_thana` = 'Khilgoan' 
and           'Dhaka' IN (a.`division`,a.`district`)

Answer 3

此代码解决了问题......

  select d.user_id,d.firstname,d.`blood_group`,a.`city_thana`,a.`division`,a.`district` from donar d natural join address a
where `blood_group` like 'Bo' and `city_thana`='Bangsal'  like `division`='DHAKA' and `district`='DHAKA'

在sql中创建四个过滤器

3 个答案: