Question

我有两个用户ID链接的表。我想从两者中创建一个新表，从每个表中提取几个字段。在一个表中，每个用户ID只有一行，而另一个表中每个用户都有几行数据。

第一个表格很简单 - 所有数据都在一行中但是，在第二个表中，数据按行排列，其中每个用户ID有几行。我想为每个用户ID找到这些行中的四个，然后将它们插入到我的表中的一列中。这是下面的代码，但它不起作用。我可以像这样嵌套子查询吗？

INSERT INTO new_table
select table1.ID, table1.user_email, table1.display_name, table2.meta-value (where table2.meta_key = ‘pet’), table2.meta-value (where table2.meta_key = ‘color'), table2.meta-value (where table2.meta_key = ‘location), table2.meta-value (where table2.meta_key = ‘house'),
from table_1, table2

Answer 1

试试这个：

INSERT INTO new_table
(SELECT 
    t1.ID, 
    t1.user_email, 
    t1.display_name, 
    (SELECT meta-value FROM table2 AS t2 WHERE t2.meta_key = 'pet' AND t2.user_id = t1.user_id), 
    (SELECT meta-value FROM table2 AS t2 WHERE t2.meta_key = 'color' AND t2.user_id = t1.user_id), 
    (SELECT meta-value FROM table2 AS t2 WHERE t2.meta_key = 'location' AND t2.user_id = t1.user_id), 
    (SELECT meta-value FROM table2 AS t2 WHERE t2.meta_key = 'house' AND t2.user_id = t1.user_id),
    FROM table_1 AS t1
)

然而，由于我没有找到有关表架构/数据的更多详细信息，因此未对其进行测试。希望这会有所帮助。

Answer 2

您可以使用查询加入：

ExamplePageAdapter examplePageAdapter = new ExamplePageAdapter(getSupportFragmentManager(),tabLayout.getTabCount());
    viewPager.setAdapter(examplePageAdapter);

Answer 3

INSERT INTO new_table
select table1.ID, table1.user_email, table1.display_name,
       max(if(table2.meta_key = 'pet', table2.meta-value, NULL)),
       max(if(table2.meta_key = 'color', table2.meta-value, NULL)),
       max(if(table2.meta_key = 'location', table2.meta-value, NULL)),
       max(if(table2.meta_key = 'house', table2.meta-value, NULL))
 from table1
 left join table2 on table2.user_id=table1.user_id
group by table1.ID, table1.user_email, table1.display_name

Answer 4

我得到了它的工作。我不知道这是否比任何其他建议更好或更差。

 INSERT INTO new_table
 SELECT t1.ID,  t1.user_email,  t1.display_name, 
        GROUP_CONCAT(IF(m.meta_key = 'pet_field', m.meta_value, NULL)) AS pet,
        GROUP_CONCAT(IF(m.meta_key = 'color_field', m.meta_value, NULL)) AS color,
        GROUP_CONCAT(IF(m.meta_key = 'location_field', m.meta_value, NULL)) AS location,
        GROUP_CONCAT(IF(m.meta_key = 'house_field', m.meta_value, NULL)) AS house
 FROM wp_users t1,
      wp_usermeta m
 WHERE u.ID = m.user_id
 GROUP BY u.ID;

从两个表创建一个表，其中数据在一个表中的行中

4 个答案: