Sql 如何在函数的UPDATE或SELECT语句中使用动态列名?
在PostgreSQL 9.1 PL/pgSQL中,给定一个查询:Sql 如何在函数的UPDATE或SELECT语句中使用动态列名?,sql,postgresql,parameter-passing,plpgsql,dynamic-sql,Sql,Postgresql,Parameter Passing,Plpgsql,Dynamic Sql,在PostgreSQL 9.1 PL/pgSQL中,给定一个查询: select fk_list.relname from ... 其中,relname类型为name(例如,“表名”) 如何获得“relname”的适当值,该值可直接用于UPDATE语句,如下所示: Update <relname> set ... 在以下情况下失败: “(”处或附近出现语法错误 第55行:更新quote_ident(r.relname) 我正在使用的完整代码: CREATE FUNCTION me
select fk_list.relname from ...
其中,relname
类型为name
(例如,“表名”)
如何获得“relname”的适当值,该值可直接用于UPDATE
语句,如下所示:
Update <relname> set ...
在以下情况下失败:
“(”处或附近出现语法错误
第55行:更新quote_ident(r.relname)
我正在使用的完整代码:
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');
我确信这种事情经常发生,但我似乎找不到使用PostgreSQL的类似方法。有更好的方法吗?在PL/pgSQL中的
UPDATE
语句中,表名必须以文本形式给出。如果要动态设置表名和列,应该使用命令并将查询字符串粘贴到盖瑟:
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。您需要动态SQL,其中已经提供了类似@Patrick的EXECUTE
。
但是,您的函数和执行部分都可以变得更加简单。特别是,使用它可以安全地连接较长的查询字符串(从第9.1页开始提供):
如果FK约束未跨越至少两列,或者列的数据类型与文本
不兼容,则函数会出错。可能与预期不符,也可能与预期不符
有关如何安全传递标识符和执行动态SQL的详细信息:
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;
CREATE OR REPLACE FUNCTION merge_children_of_icd9 (_ocicd9 text, _ocdesc text
, _ncicd9 text, _ncdesc text)
RETURNS void AS
$func$
DECLARE
_sql text;
BEGIN
FOR _sql IN
SELECT format('UPDATE %3$s SET %1$I = $3 , %2$I = $4
WHERE %1$I = $1 AND %2$I = $2'
, x.cols[1], x.cols[2], x.conrelid::regclass::text)
FROM (
SELECT c.conrelid, array_agg(a.attname ORDER BY a.attnum) AS cols
FROM pg_constraint c
JOIN pg_attribute a ON a.attrelid = c.conrelid
AND a.attnum = ANY(c.conkey)
WHERE c.confrelid = 'icd9'::regclass
AND c.contype = 'f'
GROUP BY c.oid, c.conrelid
ORDER BY c.oid
) x
LOOP
-- RAISE NOTICE '%', _sql;
EXECUTE _sql
USING _ocicd9, _ocdesc, _ncicd9, _ncdesc;
END LOOP;
END
$func$ LANGUAGE plpgsql;