sql - 我只想在 PostgreSQL 中做一个简单的循环

Question

在 PostGIS SQL 编辑器中，我只想制作一个循环以使此功能正常工作

For Loopid = 0 to 1000, then execute the following statments:

UPDATE public.globaldtm 
SET "UTM" = loopid 
WHERE rid IN (SELECT rid FROM globaldtm WHERE ST_Intersects(rast,(select geom from utm where gid =loopid)));

如何在这个 SQL 编辑器中编写一个简单的代码来使循环工作。谢谢。

Answer 1

在更新语句generate_series()的可选FROM子句中使用 set-returning函数：

UPDATE public.globaldtm 
SET UTM = loopid
FROM generate_series(0, 1000) as x(loopid) -- Added this line
WHERE rid IN (SELECT rid FROM globaldtm WHERE ST_Intersects(rast,(select geom from utm where gid =loopid)));

这是您的查询，并添加了以下行：

FROM generate_series(0, 1000) as x(loopid)

---

在 SQLFiddle 上查看类似的简化查询的现场演示。

Answer 2

创建一个函数：

CREATE OR REPLACE FUNCTION updateValuesWithLoop()
RETURNS void
AS $$
BEGIN
  FOR Loopid  IN 0..1000 LOOP
    UPDATE public.globaldtm 
       SET "UTM" = loopid 
     WHERE rid IN (SELECT rid FROM globaldtm WHERE ST_Intersects(rast,(select geom from utm where gid =loopid)));
  END LOOP;
  RETURN;
END;
$$ LANGUAGE plpgsql;

执行函数：

select updateValuesWithLoop()