如何在函数的UPDATE或SELECT语句中使用动态列名? [英] How to use dynamic column names in an UPDATE or SELECT statement in a function?
问题描述
在PostgreSQL 9.1中,PL/pgSQL给出了一个查询:
In PostgreSQL 9.1, PL/pgSQL, given a query:
select fk_list.relname from ...
,其中relname
是name
类型(例如"table_name").
where relname
is of type name
(e.g., "table_name").
如何获取"relname"的适当值,该值可以直接在UPDATE
语句中用作:
How do you get the appropriate value for "relname" that can be used directly in an UPDATE
statement as:
Update <relname> set ...
在PL/pgSQL脚本中?
within the PL/pgSQL script?
将quote_ident(r.relname)
用作:
Update quote_ident(r.relname) Set ...
失败:
<(>或附近的语法错误(( LINE 55:更新quote_ident(r.relname)....
syntax error at or near "(" LINE 55: UPDATE quote_ident(r.relname) ....
我正在使用的完整代码:
The complete code I am working with:
CREATE FUNCTION merge_children_of_icd9 (ocicd9 text,
ocdesc text, ncicd9 text, ncdesc text)
RETURNS void AS $BODY$
DECLARE
r RECORD;
BEGIN
FOR r IN
WITH fk_actions ( code, action ) AS (
VALUES ('a', 'error'),
('r', 'restrict'),
('c', 'cascade'),
('n', 'set null'),
('d', 'set default')
), fk_list AS (
SELECT pg_constraint.oid AS fkoid, conrelid, confrelid::regclass AS parentid,
conname, relname, nspname,
fk_actions_update.action AS update_action,
fk_actions_delete.action AS delete_action,
conkey AS key_cols
FROM pg_constraint
JOIN pg_class ON conrelid = pg_class.oid
JOIN pg_namespace ON pg_class.relnamespace = pg_namespace.oid
JOIN fk_actions AS fk_actions_update ON confupdtype = fk_actions_update.code
JOIN fk_actions AS fk_actions_delete ON confdeltype = fk_actions_delete.code
WHERE contype = 'f'
), fk_attributes AS (
SELECT fkoid, conrelid, attname, attnum
FROM fk_list
JOIN pg_attribute ON conrelid = attrelid AND attnum = ANY(key_cols)
ORDER BY fkoid, attnum
), fk_cols_list AS (
SELECT fkoid, array_agg(attname) AS cols_list
FROM fk_attributes
GROUP BY fkoid
)
SELECT fk_list.fkoid, fk_list.conrelid, fk_list.parentid, fk_list.conname,
fk_list.relname, fk_cols_list.cols_list
FROM fk_list
JOIN fk_cols_list USING (fkoid)
WHERE parentid = 'icd9'::regclass
LOOP
RAISE NOTICE 'now in loop. relname is %', quote_ident(r.relname);
RAISE NOTICE 'cols_list[1] is %', quote_ident(r.cols_list[1]);
RAISE NOTICE 'cols_list[2] is %', quote_ident(r.cols_list[2]);
RAISE NOTICE 'now doing update';
UPDATE quote_ident(r.relname) SET r.cols_list[1] = ncicd9, r.cols_list[2] = ncdesc
WHERE r.cols_list[1] = ocicd9 AND r.cols_list[2] = ocdesc;
RAISE NOTICE 'finished update';
END LOOP;
RETURN;
END $BODY$ LANGUAGE plpgsql VOLATILE;
-- select merge_children_of_icd9('', 'aodm type 2', '', 'aodm, type 2');
我敢肯定这种事情经常发生,但是我似乎无法使用PostgreSQL找到类似的东西.有更好的方法吗?
I'm sure this kind of thing is done often, but I can't seem to find anything like it using PostgreSQL. Is there a better way?
推荐答案
在PL/pgSQL中的UPDATE
语句中,表名必须作为文字给出.如果要动态设置表名和列,则应使用
In an UPDATE
statement in PL/pgSQL, the table name has to be given as a literal. If you want to dynamically set the table name and the columns, you should use the EXECUTE
command and paste the query string together:
EXECUTE 'UPDATE ' || quote_ident(r.relname) ||
' SET ' || quote_ident(r.cols_list[1]) || ' = $1, ' ||
quote_ident(r.cols_list[2]) || ' = $2' ||
' WHERE ' || quote_ident(r.cols_list[1]) || ' = $3 AND ' ||
quote_ident(r.cols_list[2]) || ' = $4'
USING ncicd9, ncdesc, ocicd9, ocdesc;
USING
子句只能用于替换数据值,如上所示.
The USING
clause can only be used for substituting data values, as shown above.
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