使用 H2 中 CTE 的结果集进行更新

Question

我正在尝试使用 CTE 的结果集更新表。参考this question

如果table_b是这样的CTE结果，查询是否有效

With table_b as (select a_id from table_x)
update table_a a
set a.b_id = (select b.id from table_b b where b.a_id = a.id)
where a.id = (select b.a_id from table_b b where b.a_id = a.id)

Answer 1

id也需要选择，否则b.id将找不到。

with table_b as (select id, a_id from table_x)
update table_a a
set a.b_id = (select b.id from table_b b where b.a_id = a.id)
where a.id = (select b.a_id from table_b b where b.a_id = a.id)

您还应该考虑使用MERGE 命令而不是UPDATE，它可能更有效。

with table_b as (select id, a_id from table_x)
merge into table_a using table_b on table_a.id = table_b.a_id
when matched then update set b_id = table_b.id;