标签：ann 简单 dmi ued 需要 指定 time 级联 div
如果返回一个 数字或者字符 比较简单，那么多行多列怎么办呢，分为以下几种情况 【东西很多，这里只做简单列举】
又分为几种方式
1. return next，用在 for 循环中
CREATE OR REPLACE FUNCTION funcname ( in_id integer) RETURNS SETOF varchar as $$ DECLARE v_name varchar; BEGIN for v_name in ( (select name from test_result1 where id = in_id) union (select name from test_result2 where id = in_id) ) loop RETURN NEXT v_name; end loop; return; END; $$ LANGUAGE PLPGSQL;
注意
1. 循环外还有个 return
2. 需要实现声明 v_name
2. return query，无需 for 循环
CREATE OR REPLACE FUNCTION funcname ( in_id integer) RETURNS SETOF varchar as $$ DECLARE v_rec RECORD; BEGIN return query ( (select name from test_result1 where id = in_id) union (select name from test_result2 where id = in_id) ); return; END; $$ LANGUAGE PLPGSQL;
注意：如果 返回类型为 setof，最好用如下方法
RETURN QUERY EXECUTE SQL
不要这么用
execute sql into out; return out;
也有多种方式
1. 使用 return next 和 setof record ，需要 for 循环
CREATE OR REPLACE FUNCTION funcname ( in_id integer) RETURNS SETOF RECORD as $$ DECLARE v_rec RECORD; BEGIN for v_rec in ( (select id , name from test_result1 where id = in_id) union (select id , name from test_result2 where id = in_id) )loop RETURN NEXT v_rec; end loop; return; END; $$ LANGUAGE PLPGSQL;
注意
1. 读取表的整行数据时才能用 record
2. 如果读取的数据不是整行，需要自定义 复合数据类型，否则会报如下错误
ERROR: a column definition list is required for functions returning "record"
定义复合类型，示例如下
create type myout2 as ( road_num int, freq bigint ); create or replace function test(car text, time1 text, time2 text) returns setof myout2 as $$ declare array1 text[]; array2 text[]; len1 integer; len2 integer; x integer; y integer; road_str text; car_str text; sql text; i myout2; begin -- vin 号拼接 select regexp_split_to_array(car, ‘,‘) into array2; select array_length(array2, 1) into len2; car_str := ‘‘; y := 1; while y <= len2 loop car_str := car_str || quote_literal(array2[y]) || ‘,‘; y := y + 1; end loop; -- sql 拼接 sql := ‘select road_number, sum(frequency) from heat_map where date_key >= ‘‘‘ || time1 || ‘-01‘‘ and date_key <=‘‘‘ || time2 || ‘-20‘‘ and vin in (‘ || rtrim(car_str, ‘,‘) || ‘)group by road_number;‘; --execute sql into out; for i in execute sql loop return next i; end loop; return; end $$ language plpgsql;
在执行时可能会报如下错误
ERROR: set-valued function called in context that cannot accept a set
解决方法
select funcname(arg); --改为 select * from funcname(arg);
2. return query，无需 for 循环
CREATE OR REPLACE FUNCTION funcname ( in_id integer) RETURNS SETOF RECORD as $$ DECLARE v_rec RECORD; BEGIN return query ( (select id , name from test_result1 where id = in_id) union (select id , name from test_result2 where id = in_id) ); return; END; $$ LANGUAGE PLPGSQL;
3. 使用 out 输出参数
CREATE OR REPLACE FUNCTION funcname ( in_id integer,out o_id integer,out o_name varchar) RETURNS SETOF RECORD as $$ DECLARE v_rec RECORD; BEGIN for v_rec in ( (select id , name from test_result1 where id = in_id) union (select id , name from test_result2 where id = in_id) )loop o_id := v_rec.id; o_name := v_rec.name; RETURN NEXT ; end loop; return; END; $$ LANGUAGE PLPGSQL;
我们可以看到上面无论是单列多行还是多列多行，都用到了 return next 和 return query 方法
在 plpgsql 中，如果存储过程返回 setof sometype，则返回值必须在 return next 或者 return query 中声明，然后有一个不带参数的 retrun 命令，告诉函数执行完毕； 【setof 就意味着 多行】
用法如下
RETURN NEXT expression; RETURN QUERY query; RETURN QUERY EXECUTE command-string [ USING expression [, ... ] ];
return next 可以用于标量和复合类型数据；
return query 命令将查询到的一条结果追加到函数的结果集中；
二者在单一集合返回函数中自由混合，在这种情况下，结果将被级联。【有待研究】
return query execute 是 return query 的变形，它指定 sql 将被动态执行；
return query select road_number, sum(frequency) from heat_map group by road_number; --这样可以 sql := ‘select road_number, sum(frequency) from heat_map group by road_number‘; return query sql; --这样不行
参考资料：
https://blog.csdn.net/victor_ww/article/details/44415895 postgresql自定义类型并返回数组
https://blog.csdn.net/weixin_42767321/article/details/92992935 PG return next & return query
https://blog.csdn.net/luojinbai/article/details/45487373 PostgreSQL function返回多列多行
https://www.cnblogs.com/xiongsd/archive/2013/06/05/3118704.html 返回结果集多列和单列的例子
https://www.cnblogs.com/lottu/p/7404722.html PostgreSQL存储过程(1)-基于SQL的存储过程
https://blog.csdn.net/pg_hgdb/article/details/79692749 Postgresql动态SQL
https://stackoverflow.com/questions/40864464/postgresql-pgadmin-error-return-cannot-have-a-parameter-in-function-returning-s/40864898 postgresql, pgadmin error RETURN cannot have a parameter in function returning set
https://blog.csdn.net/qq_42535651/article/details/92089510 postgresql存储过程输出参数
https://www.cnblogs.com/winkey4986/p/6437811.html
https://www.cnblogs.com/lottu/p/7405829.html PostgreSQL存储过程(3)-流程控制语句
标签：ann 简单 dmi ued 需要 指定 time 级联 div
原文地址：https://www.cnblogs.com/yanshw/p/12120473.html
