我正在尝试获取列的值,以便将其插入到包含插入行的列名称和列值的表中,但是,我无法获取该列的值我需要。通常,我可以使用 value := NEW.column_name
但每个表都有一个唯一的键列名称,该名称位于表名称本身中(我知道,这很糟糕),但我已经有办法获取我想要的列名称,它正在获取该列的新值,这就是问题所在。
CREATE OR REPLACE FUNCTION trgfn_keyvalue_insert()
RETURNS trigger AS
$BODY$
DECLARE
key_column_value character varying;
key_column_name character varying;
part text;
part_array text[] := array['prefix_','_suffix'];
BEGIN
key_column_name := TG_TABLE_NAME; --parsing the table name to get the desired column name
FOREACH part IN ARRAY part_array LOOP
key_column_name = regexp_replace(cat, part, '');
END loop;
IF TG_OP = 'INSERT' THEN
EXECUTE 'SELECT $1 FROM $2' --This is where I'd like to get the
INTO key_column_value --value of the column
USING key_column_name, NEW;
INSERT INTO inserted_kvp
(table_name, key, value)
VALUES
(TG_TABLE_NAME, key_column_name, key_column_value);
END IF;
RETURN NEW;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
所以,当我插入表时:
CREATE TABLE prefix_kvp1_suffix AS id SERIAL, kvp1 CHARACTER VARYING;
CREATE TABLE prefix_kvp2_suffix AS id SERIAL, kvp2 CHARACTER VARYING;
INSERT INTO prefix_kvp1_suffix VALUES (1, 'value1');
INSERT INTO prefix_kvp2_suffix VALUES (1, 'value2');
我想要 inserted_kvp
表具有以下内容:
| table_name |key |value |
--------------------------------
|prefix_kvp1_suffix|kvp1|value1|
|prefix_kvp2_suffix|kvp2|value2|
相反,我在插入时收到以下错误:
ERROR: syntax error at or near "$2"
LINE 1: SELECT $1 FROM $2
^
QUERY: SELECT $1 FROM $2
CONTEXT: PL/pgSQL function worldmapkit.trgfn_keyvalue_insert() line 13 at EXECUTE statement
我尝试了使用 EXECUTE format()
获取此值的不同变体和其他一些方法,但我仍然没有任何运气。如有任何帮助,我们将不胜感激!
最佳答案
经过一番折腾,我找到了问题的答案。上述 EXECUTE 语句的正确语法是:
EXECUTE format('SELECT $1.%I', key_column_name)
INTO key_column_value
USING NEW;
这将获取新记录的列值。希望这会对处于类似情况的人有所帮助。
关于dynamic - Postgres : How to get the value of a dynamic column from triggers,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/25899446/