[英]How to insert values from another table in PostgreSQL?
我有一个引用其他表的表:
CREATE TABLE scratch
(
id SERIAL PRIMARY KEY,
name TEXT NOT NULL,
rep_id INT NOT NULL REFERENCES reps,
term_id INT REFERENCES terms
);
CREATE TABLE reps (
id SERIAL PRIMARY KEY,
rep TEXT NOT NULL UNIQUE
);
CREATE TABLE terms (
id SERIAL PRIMARY KEY,
terms TEXT NOT NULL UNIQUE
);
我希望在给定name , rep和terms值的情况下添加一个新记录来临时,即我既没有相应的rep_id也没有term_id 。
现在我唯一的想法是:
insert into scratch (name, rep_id, term_id)
values ('aaa', (select id from reps where rep='Dracula' limit 1), (select id from terms where terms='prepaid' limit 1));
我的问题是这个。 我正在尝试使用参数化查询 API(来自使用 node-postgres 包的节点),其中插入查询如下所示:
insert into scratch (name, rep_id, term_id) values ($1, $2, $3);
然后将 $1、$2 和 $3 的值数组作为单独的参数传递。 最后,当我对参数化查询感到满意时,我的想法是将它们提升为准备好的语句,以利用最有效和最安全的方式查询数据库。
但是,我很困惑如何在我的示例中执行此操作,其中必须对不同的表进行子查询。
PS 我正在使用 PostgreSQL 9.2 并且对 PostgreSQL 特定的解决方案没有问题。
编辑 1
C:\Users\markk>psql -U postgres
psql (9.2.4)
WARNING: Console code page (437) differs from Windows code page (1252)
8-bit characters might not work correctly. See psql reference
page "Notes for Windows users" for details.
Type "help" for help.
postgres=# \c dummy
WARNING: Console code page (437) differs from Windows code page (1252)
8-bit characters might not work correctly. See psql reference
page "Notes for Windows users" for details.
You are now connected to database "dummy" as user "postgres".
dummy=# DROP TABLE scratch;
DROP TABLE
dummy=# CREATE TABLE scratch
dummy-# (
dummy(# id SERIAL NOT NULL PRIMARY KEY,
dummy(# name text NOT NULL UNIQUE,
dummy(# rep_id integer NOT NULL,
dummy(# term_id integer
dummy(# );
NOTICE: CREATE TABLE will create implicit sequence "scratch_id_seq" for serial column "scratch.id"
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "scratch_pkey" for table "scratch"
NOTICE: CREATE TABLE / UNIQUE will create implicit index "scratch_name_key" for table "scratch"
CREATE TABLE
dummy=# DEALLOCATE insert_scratch;
ERROR: prepared statement "insert_scratch" does not exist
dummy=# PREPARE insert_scratch (text, text, text) AS
dummy-# INSERT INTO scratch (name, rep_id, term_id)
dummy-# SELECT $1, r.id, t.id
dummy-# FROM reps r, terms t
dummy-# WHERE r.rep = $2 AND t.terms = $3
dummy-# RETURNING id, name, $2 rep, $3 terms;
PREPARE
dummy=# DEALLOCATE insert_scratch2;
ERROR: prepared statement "insert_scratch2" does not exist
dummy=# PREPARE insert_scratch2 (text, text, text) AS
dummy-# INSERT INTO scratch (name, rep_id, term_id)
dummy-# VALUES ($1, (SELECT id FROM reps WHERE rep=$2 LIMIT 1), (SELECT id FROM terms WHERE terms=$3 LIMIT 1))
dummy-# RETURNING id, name, $2 rep, $3 terms;
PREPARE
dummy=# EXECUTE insert_scratch ('abc', 'Snowhite', '');
id | name | rep | terms
----+------+-----+-------
(0 rows)
INSERT 0 0
dummy=# EXECUTE insert_scratch2 ('abc', 'Snowhite', '');
id | name | rep | terms
----+------+----------+-------
1 | abc | Snowhite |
(1 row)
INSERT 0 1
dummy=# EXECUTE insert_scratch ('abcd', 'Snowhite', '30 days');
id | name | rep | terms
----+------+----------+---------
2 | abcd | Snowhite | 30 days
(1 row)
INSERT 0 1
dummy=# EXECUTE insert_scratch2 ('abcd2', 'Snowhite', '30 days');
id | name | rep | terms
----+-------+----------+---------
3 | abcd2 | Snowhite | 30 days
(1 row)
INSERT 0 1
dummy=#
编辑 2
我们可以利用rep_id
是必需的事实,即使terms_id
是可选的,并使用以下版本的 INSERT-SELECT:
PREPARE insert_scratch (text, text, text) AS
INSERT INTO scratch (name, rep_id, term_id)
SELECT $1, r.id, t.id
FROM reps r
LEFT JOIN terms t ON t.terms = $3
WHERE r.rep = $2
RETURNING id, name, $2 rep, $3 terms;
但是这个版本有两个问题:
terms
值(即'')和无效的terms
值(即terms表中完全缺失的非空值)之间没有区别。 两者都被视为缺失项。 (但是带有两个子查询的 INSERT 遇到了同样的问题)rep
的事实。 但是如果rep_id
也是可选的呢?编辑 3
找到了第 2 项的解决方案 - 消除了对所需代表的依赖。 另外,使用 WHERE 语句的问题是,如果 rep 无效,sql 不会失败 - 它只插入 0 行,而我想在这种情况下显式失败。 我的解决方案只是使用一个虚拟的单行 CTE:
PREPARE insert_scratch (text, text, text) AS
WITH stub(x) AS (VALUES (0))
INSERT INTO scratch (name, rep_id, term_id)
SELECT $1, r.id, t.id
FROM stub
LEFT JOIN terms t ON t.terms = $3
LEFT JOIN reps r ON r.rep = $2
RETURNING id, name, rep_id, term_id;
如果 rep 丢失或无效,此 sql 将尝试将 NULL 插入到 rep_id 字段中,并且由于该字段NOT NULL
会引发错误 - 正是我需要的。 如果我进一步决定让 rep 可选——没问题,同样的 SQL 也适用于此。
INSERT into scratch (name, rep_id, term_id)
SELECT 'aaa'
, r.id
, t.id
FROM reps r , terms t -- essentially a cross join
WHERE r.rep = 'Dracula'
AND t.terms = 'prepaid'
;
注意事项:
LIMIT
s,因为 r.rep 和 t.terms 是唯一的(候选键)FROM a CROSS JOIN b
替换FROM a, b
FROM a CROSS JOIN b
scratch
表可能需要on (rep_id, term_it)
的UNIQUE
约束on (rep_id, term_it)
term_id
可空性是有问题的)更新:与文档中的准备查询相同
PREPARE hoppa (text, text,text) AS
INSERT into scratch (name, rep_id, term_id)
SELECT $1 , r.id , t.id
FROM reps r , terms t -- essentially a cross join
WHERE r.rep = $2
AND t.terms = $3
;
EXECUTE hoppa ('bbb', 'Dracula' , 'prepaid' );
SELECT * FROM scratch;
UPDATE2:测试数据
DROP SCHEMA tmp CASCADE;
CREATE SCHEMA tmp ;
SET search_path=tmp;
CREATE TABLE reps ( id SERIAL PRIMARY KEY, rep TEXT NOT NULL UNIQUE);
CREATE TABLE terms ( id SERIAL PRIMARY KEY, terms TEXT NOT NULL UNIQUE);
CREATE TABLE scratch ( id SERIAL PRIMARY KEY, name TEXT NOT NULL, rep_id INT NOT NULL REFERENCES reps, term_id INT REFERENCES terms);
INSERT INTO reps(rep) VALUES( 'Dracula' );
INSERT INTO terms(terms) VALUES( 'prepaid' );
结果:
NOTICE: drop cascades to 3 other objects
DETAIL: drop cascades to table tmp.reps
drop cascades to table tmp.terms
drop cascades to table tmp.scratch
DROP SCHEMA
CREATE SCHEMA
SET
CREATE TABLE
CREATE TABLE
CREATE TABLE
INSERT 0 1
INSERT 0 1
INSERT 0 1
PREPARE
INSERT 0 1
id | name | rep_id | term_id
----+------+--------+---------
1 | aaa | 1 | 1
2 | bbb | 1 | 1
(2 rows)
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.