我有两个这样的表:
CREATE TABLE table1_lang
(
id serial NOT NULL,
lang1 character varying,
lang2 character varying,
...
)
CREATE TABLE table2_lang
(
id serial NOT NULL,
table1_id NOT NULL,
lang1 character varying,
lang2 character varying,
...
)
每个lang列都包含不同语言的名称 . 我想创建一个函数,从table1_lang返回所选的lang(如果存在) . 如果table1_lang中不存在该名称,则该函数应从table2_lang返回该名称 .
到目前为止,我已经用plpgsql中的这个函数解决了我的问题:
CREATE OR REPLACE FUNCTION get_name(integer, text)
RETURNS character varying AS
$BODY$
DECLARE
in_id ALIAS FOR $1;
lang ALIAS FOR $2;
table1_name varchar;
table2_name varchar;
BEGIN
IF lang IS NOT NULL AND lang = 'lang1' THEN
SELECT a.lang1 INTO table1_name
FROM table1_lang a
WHERE a.id = in_id;
IF table1_name IS NOT NULL AND length(table1_name) > 0 THEN
RETURN table1_name;
ELSE
SELECT a.lang1 INTO table2_name
FROM table2_lang a
WHERE a.table1_id = in_id;
IF table2_name IS NOT NULL AND length(table2_name) > 0 THEN
RETURN table2_name;
END IF;
END IF;
END IF;
IF lang IS NOT NULL AND lang = 'lang2' THEN
SELECT a.lang2 INTO table1_name
FROM table1_lang a
WHERE a.id = in_id;
IF table1_name IS NOT NULL AND length(table1_name) > 0 THEN
RETURN table1_name;
ELSE
SELECT a.lang2 INTO table2_name
FROM table2_lang a
WHERE a.table1_id = in_id;
IF table2_name IS NOT NULL AND length(table2_name) > 0 THEN
RETURN table2_name;
END IF;
END IF;
END IF;
...
IF table2_name IS NULL OR length(table2_name) = 0 THEN
RETURN NULL;
END IF;
END
$BODY$
LANGUAGE plpgsql VOLATILE STRICT
COST 100;
ALTER FUNCTION get_name(integer, text) OWNER TO postgres;
但是我想知道是否有可能在plpgsql或PostgreSQL中可用的其他语言中创建一个以列为输入参数的函数?
1 回答
它可以在plpgsql函数中使用 . 但是,如果标识符(包括列名称)是参数化的,则必须构建动态SQL并使用
EXECUTE
执行它 . 在the manual here中了解相关内容 . 注意不要通过这样做来允许SQL注入 . 利用quote_ident() or format() .我用链接和解释写了几个类似的答案 . 尝试this one作为开始或this one .