将JOIN添加到table 2。

select a.id, a.first_name, a.middle_name, b.last_name
from table1 a
left join table2 b
  on a.id = b.id
where a.id < 4

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更新

根据您最近对问题的编辑，您可以使用conditional aggregation来实现这些更新的结果。

select 
 a.id, 
 max(case when a.entry = 'first_name' then a.result end) as first_name,
 max(case when b.entry = 'middle_name' then b.result end) as middle_name, 
 max(case when b.entry = 'last_name' then b.result end) as last_name
from table1 a
left join table2 b
  on a.id = b.id
group by a.id;

型
| ID|名字|中间名|姓氏（_N）|
| --|--|--|--|
| 1 |琳达|玛丽|Jackson|
| 2 |玛丽|爱丽丝||
| 3 |约翰|史蒂文|汤姆森|
View on DB Fiddle

这可以通过LEFT JOIN来实现：

Select t1.id, t1.first_name, t1.middle_name, t2.last_name
from table1 t1
left join table2 t2 on t1.id = t2.id
where t1.id < 4

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根据您最近的编辑，数据结构已更改为实体-属性-值模型（EAV）。
我也使用了条件聚合，但只应用于table 2以获取中间名和姓氏：

select t1.*, t2.middle_name, t2.last_name
from (
  select id, result as first_name
  from table1
  where entry = 'first_name'
) as t1
left join (
  select id, max(case when entry = 'middle_name' then result end) as middle_name,
             max(case when entry = 'last_name' then result end) as last_name
  from table2
  group by id
) as t2 on t1.id = t2.id;

型
Demo here