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Question

我修改了我的函数来执行一些 json 对象

cursor loop in PostgreSQL

我有查询返回以下结果

SELECT asn."Id",asn."UserId",asn."ActivityId",pd."DataSourceId",ad."Dump"
   FROM "Development"."ActivitySession" as asn inner join "Development"."PersonDataSource" as pd on pd."UserId" = asn."UserId" inner join "Development"."ActivitySessionDump" as ad 
   on asn."Id"=ad."ActivitySessionId" where asn."CreatedAt" between now() - interval '5 days' and now() and asn."ActivityId"=1  and pd."DataSourceId"=1



Id                        UserId    ActId   DId  Dump
42594890910270849   42031336811660529   1   1   {"activities-steps":[{"dateTime":"2016-10-17","value":"4023"}]}
42595097786975653   42031336811660529   1   1   {"activities-steps":[{"dateTime":"2016-10-17","value":"4023"}]}
42597154682570183   42031336811660529   1   1   {"activities-steps":[{"dateTime":"2016-10-17","value":"5388"}]}
42602824351352325   42031336811660529   1   1   {"activities-steps":[{"dateTime":"2016-10-18","value":"0"}]}
42605659177354793   42031336811660529   1   1   {"activities-steps":[{"dateTime":"2016-10-18","value":"0"}]}
42611328851117671   42031336811660529   1   1   {"activities-steps":[{"dateTime":"2016-10-18","value":"0"}]}

我在下面写了一个函数

CREATE OR REPLACE FUNCTION ThirdPartyDataParse()
RETURNS text AS $$
DECLARE 
sessionid NO SCROLL CURSOR FOR SELECT asn."Id",asn."UserId",asn."ActivityId",pd."DataSourceId",ad."Dump"
   FROM "Development"."ActivitySession" as asn inner join "Development"."PersonDataSource" as pd on pd."UserId" = asn."UserId" inner join "Development"."ActivitySessionDump" as ad 
   on asn."Id"=ad."ActivitySessionId" where asn."CreatedAt" between now() - interval '5 days' and now() and asn."ActivityId"=1  and pd."DataSourceId"=1 for read only;
titles TEXT DEFAULT '';
rec record;
jsonrec record;
 BEGIN
 OPEN sessionid;
loop

FETCH sessionid INTO rec;
--raise notice '%d',rec."UserId";
   if not found then
        exit ;
   end if;
--titles := titles || ',' || rec."Dump";
 EXECUTE 'SELECT rec."Dump"::json#>''{activities-steps,0}''->>''value''' INTO jsonrec;
titles := titles || ',' || jsonrec."steps";
end loop;
return titles;
END;
$$ LANGUAGE plpgsql;

但我无法执行

EXECUTE 'SELECT rec."dump"::json#>''{activities-steps,0}''->>''value''' INTO jsonrec;

rec."dump" 这里等于 {"activities-steps":[{"dateTime":"2016-10-17","value":"4023"}]}，所以我的查询就像

SELECT '{"activities-steps":[{"dateTime":"2016-10-17","value":"4023"}]}'::json#>'{activities-steps,0}'->>'value' as steps;

但我无法执行这个内部函数错误是：

Error in query: ERROR: missing FROM-clause entry for table "rec"
LINE 1: SELECT rec."Dump"::json#>'{activities-steps,0}'->>'value'
QUERY: SELECT rec."Dump"::json#>'{activities-steps,0}'->>'value'
CONTEXT: PL/pgSQL function thirdpartydataparse() line 19 at EXECUTE statement

Answer 1

您不能在命令字符串中包含对 PL/pgSQL 变量的引用。 SQL 解析器不知道这些变量，因此它假定您正在请求表 rec 的属性 "Dump"，然后如果该表没有 FROM 子句，则会抱怨。

你需要像这样使用EXECUTE ... USING：

EXECUTE 'SELECT $1::json#>''{activities-steps,0}''->>''value'''
   INTO jsonrec USING rec."Dump";