postgresql:使用游标从一个数据库提取数据并将其插入另一个数据库
这是另一个使用游标的算法,但我很难修复它的错误postgresql:使用游标从一个数据库提取数据并将其插入另一个数据库,postgresql,plpgsql,Postgresql,Plpgsql,这是另一个使用游标的算法,但我很难修复它的错误 CREATE OR REPLACE FUNCTION extractstudent() RETURNS VOID AS $BODY$ DECLARE studcur SCROLL cursor FOR SELECT fname, lname, mname, address FROM student; BEGIN open studcur; Loop --fetching 1 row at a time
CREATE OR REPLACE FUNCTION extractstudent()
RETURNS VOID AS
$BODY$
DECLARE
studcur SCROLL cursor FOR SELECT fname, lname, mname, address FROM student;
BEGIN
open studcur;
Loop
--fetching 1 row at a time
FETCH First FROM studcur;
--every row fetched is being inserted to another database on the local site
--myconT is the name of the connection to the other database in the local site
execute 'SELECT * from dblink_exec(''myconT'', ''insert into temp_student values(studcur)'')';
--move to the next row and execute again
move next from studcur;
--exit when the row content is already empty
exit when studcur is null;
end loop;
close studcur;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
ALTER FUNCTION extractstudent() OWNER TO postgres;
为什么不自己试一下,根据错误,你可以试着一步一步地解决它们 在postgresql或pl/pgsql中很少需要显式使用游标。您所编写的内容看起来很像SQL Server游标循环构造,您不需要这样做。此外,您可以使用PERFORM而不是EXECUTE来运行查询并放弃结果:这将避免每次重新解析查询,尽管它无法避免每次dblink解析查询 您可以执行以下操作:
DECLARE
rec student%rowtype;
BEGIN
FOR rec IN SELECT * FROM student
LOOP
PERFORM dblink_exec('myconT',
'insert into temp_student values ('
|| quote_nullable(rec.fname) || ','
|| quote_nullable(rec.lname) || ','
|| quote_nullable(rec.mname) || ','
|| quote_nullable(rec.address) || ')');
END LOOP;
END;
抱歉,我不能真正理解学生%rowtype和部分->“| | quote|nullablerec.fname | |”、“| | quote| nullablerec.lname | |”、“| | quote| nullablerec.mname |”,“| | quote | nullablerec.address | | |”您能解释一下这一部分吗?student%rowtype是自动创建的记录结构类型,格式与student表相同。quote_nullable接受字符串值并输出引用值,适合包含在SQL语句中。