使用Postgres一次在3个表中插入数据

Question

我想通过一个查询将数据插入到3个表中.
我的表如下所示:

CREATE TABLE sample (
   id        bigserial PRIMARY KEY,
   lastname  varchar(20),
   firstname varchar(20)
);

CREATE TABLE sample1(
   user_id    bigserial PRIMARY KEY,
   sample_id  bigint REFERENCES sample,
   adddetails varchar(20)
);

CREATE TABLE sample2(
   id      bigserial PRIMARY KEY,
   user_id bigint REFERENCES sample1,
   value   varchar(10)
);

我将获得一个密钥以换取每次插入,我需要在下一个表中插入该密钥.
我的查询是:

insert into sample(firstname,lastname) values('fai55','shaggk') RETURNING id;
insert into sample1(sample_id, adddetails) values($id,'ss') RETURNING user_id;
insert into sample2(user_id, value) values($id,'ss') RETURNING id;

但是,如果我运行单个查询,他们只是向我返回值,我不能立即在下一个查询中重用它们.

怎么做到这一点？

Answer 1

使用数据修改CTE:

WITH ins1 AS (
   INSERT INTO sample(firstname, lastname)
   VALUES ('fai55', 'shaggk')
-- ON     CONFLICT DO NOTHING                -- optional addition in Postgres 9.5+
   RETURNING id AS user_id
   )
, ins2 AS (
   INSERT INTO sample1 (user_id, adddetails)
   SELECT user_id, 'ss' FROM ins1
   -- RETURNING user_id                      -- only if used in turn
   )
INSERT INTO sample2 (user_id, value)         -- same here
SELECT user_id, 'ss' FROM ins1;

每个插入都取决于之前的插入.如果没有从前一个插入返回任何行INSERT,SELECT则确保在子表中不插入任何内容.(相关:VALUESPostgres 9.5+中的条款)
它也更短更快.

通常,在一个地方提供完整的数据行更方便:

WITH data(firstname, lastname, adddetails, value) AS (
   VALUES                                 -- provide data here
      (text 'fai55', text 'shaggk', text 'ss', text 'ss2')  -- see below
       --  more?                          -- works for multiple input rows
   )
, ins1 AS (
   INSERT INTO sample (firstname, lastname)
   SELECT firstname, lastname FROM data   -- DISTINCT? see below
   ON     CONFLICT DO NOTHING             -- requires UNIQUE constraint
   RETURNING firstname, lastname, id AS sample_id
   )
, ins2 AS (
   INSERT INTO sample1 (sample_id, adddetails)
   SELECT sample_id, adddetails
   FROM   data
   JOIN   ins1 USING (firstname, lastname)
   RETURNING sample_id, user_id
   )
INSERT INTO sample2 (user_id, value)
SELECT user_id, value
FROM   data
JOIN   ins1 USING (firstname, lastname)
JOIN   ins2 USING (sample_id);

您可能需要在单独的INSERT表达式中显式类型转换(与ON CONFLICT附加到INSERT 的表达式相反,其中数据类型从目标表派生.

如果多行可以相同VALUES,则可能需要为第一个插入折叠重复:

...
INSERT INTO sample (firstname, lastname)
SELECT DISTINCT firstname, lastname FROM data
...

您可以使用(临时)表作为数据源而不是CTE VALUES.

相关,更多细节:

• 如何在PostgreSQL中使用RETURNING和ON CONFLICT？
• SELECT或INSERT是否容易出现竞争条件？

Answer 2

像这样的东西

with first_insert as (
   insert into sample(firstname,lastname) 
   values('fai55','shaggk') 
   RETURNING id
), 
second_insert as (
  insert into sample1( id ,adddetails) 
  values
  ( (select id from first_insert), 'ss')
  RETURNING user_id
)
insert into sample2 ( id ,adddetails) 
values 
( (select user_id from first_insert), 'ss');

由于sample2不需要从插入到生成的id ,我returning从最后一个插入中删除了该子句.

Answer 3

通常,您使用事务来避免编写复杂的查询.

http://www.postgresql.org/docs/current/static/sql-begin.html

http://dev.mysql.com/doc/refman/5.7/en/commit.html

假设你的Postgres标签是正确的,你也可以使用CTE.例如:

with sample_ids as (
  insert into sample(firstname, lastname)
  values('fai55','shaggk')
  RETURNING id
), sample1_ids as (
  insert into sample1(id, adddetails)
  select id,'ss'
  from sample_ids
  RETURNING id, user_id
)
insert into sample2(id, user_id, value)
select id, user_id, 'val'
from sample1_ids
RETURNING id, user_id;

Answer 4

您可以在示例表上创建插入后触发器以插入到其他两个表中。

我发现这样做的唯一问题是，您无法插入 adddetails ，它始终为空，或者在本例中为 ss。无法将实际上不在示例表中的列插入到示例中，因此您无法将其与初始插入一起发送。

另一种选择是创建一个存储过程来运行插入。

您的问题标记为 mysql 和 postgressql 我们在这里讨论的是哪个数据库？