如何在plpgsql过程中有条件地运行查询

Question

我的一些数据模型有一些关系，必须在对其子进行更改时保持更新，例如多点位置，这些位置是许多必须更新点位置的子项的集合如果一个孩子搬迁。这种关系有很多种，我想要在一个触发器+程序中处理这些关系的完整性，在更新父母受影响关系的相关字段时触发以下过程。

我如何格式化这些查询和条件，使得它完成以下操作：

CREATE TABLE parents (
    id BIGSERIAL PRIMARY KEY, 
    caption TEXT, 
    title TEXT, 
    tags CHARACTER VARYING(32)[] DEFAULT '{}', 
    rating SMALLINT DEFAULT 0 
) 
CREATE TABLE children (
    id BIGSERIAL PRIMARY KEY, 
    tags CHARACTER VARYING(32)[] DEFAULT '{}', 
    rating SMALLINT DEFAULT 0 
) 
CREATE TABLE parent_children (
    parent_id BIGINT, 
    child_id BIGINT 
) 

CREATE OR REPLACE FUNCTION child_updated_func() RETURNS TRIGGER AS $$ 
    BEGIN 
     IF (OLD.tags != NEW.tags) 
      UPDATE parents 
      SET tags = tags || NEW.tags 
      WHERE 
       parent_children.child_id = NEW.id 
       AND parents.id = parent_children.parent_id; 
     IF (OLD.rating != NEW.rating) 
      UPDATE parents 
      SET rating = MAX(parent_children.rating) 
      FROM parent_children 
      WHERE 
       parent_children.child_id = NEW.id 
       AND parents.id = parent_children.parent_id; 
     RETURN NEW; 
    END 
$$ LANGUAGE plpgsql; 

CREATE TRIGGER child_updated 
    AFTER UPDATE ON children 
    FOR EACH ROW 
    EXECUTE PROCEDURE child_updated_func(); 

Answer 1

你可能想是这样的：

CREATE OR REPLACE FUNCTION func() RETURNS TRIGGER AS $$ 
    BEGIN 
     IF (OLD.tags != NEW.tags) THEN 
      UPDATE parents 
      SET tags = tags || NEW.tags 
      WHERE 
       parent_children.child_id = NEW.id 
       AND parents.id = parent_children.parent_id; 
     END IF; 
     IF (OLD.rating != NEW.rating) 
      UPDATE parents 
      SET rating = MAX(parent_children.rating) 
      FROM parent_children 
      WHERE 
       parent_children.child_id = NEW.id 
       AND parents.id = parent_children.parent_id; 
     END IF; 
     RETURN NEW; 
    END 
$$ LANGUAGE plpgsql;