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database - 将变量声明为 ROWTYPE - 触发函数

问题描述

在这个问题中，我创建了一个名为 groups(id, name, group_id INTEGER NULLABLE,class_id INTEGER NULLABLE) 的表，其逻辑是对组、类和子类之间的数据进行分类。一个组有很多类，一个类有很多子类。我想在 plpgsql 中创建一个触发器函数，以保证插入或更新数据之前的一些条件。

数据分类条件如下。

.

CREATE FUNCTION emp_subclasse() RETURNS trigger AS $subclasse_verification$
DECLARE
  group groups%ROWTYPE;
  classe groups%ROWTYPE;
  class_group groups%ROWTYPE;
BEGIN
  group =(SELECT * FROM groups WHERE id=NEW.group_id);
  classe =(SELECT * FROM groups WHERE id=NEW.clazz_id);
  class_group =(SELECT * FROM groups WHERE id=classe.group_id);
  IF NEW.clazz_id IS NOT NULL THEN
      IF (classe.group_id) IS NULL THEN
          RAISE EXCEPTION 'A CLASS MUST POINT TO A GROUP';
      ELSIF classe.group_id IS NOT NULL THEN
          NEW.group_id = classe.group_id;
          IF class_group.group_id IS NOT NULL OR class_group.clazz_id IS NOT NULL THEN
              RAISE EXCEPTION 'A GROUP CANNOT HAVE A GROUP_ID OR CLASS_ID POINTED';
          END IF;
      END IF;
      IF classe.clazz_id IS NOT NULL THEN
          RAISE EXCEPTION 'CANNOT CLASSIFY A CLASS AS A SUBCLASS';
      END IF;
  ELSIF NEW.clazz_id IS NULL THEN
      IF NEW.group_id IS NOT NULL THEN
          IF group.group_id IS NOT NULL OR grupo.clazz_id IS NOT NULL THEN
              RAISE EXCEPTION 'A GROUP CANNOT HAVE A GROUP_ID OR CLASS_ID POINTED';
          END IF;
      END IF;
  END IF;
END;
$subclasse_verification$ LANGUAGE 'plpgsql';

CREATE TRIGGER subclasse_verification BEFORE INSERT OR UPDATE ON groups
  FOR EACH ROW EXECUTE PROCEDURE emp_subclasse();

但是，当我尝试插入值时，出现错误[2018-11-20 16:35:20] [42601] ERROR: subquery must return only one column [2018-11-20 16:35:20] WHERE: PL/pgSQL function emp_subclasse() line 7 at assignment

标签： databasepostgresqlplpgsqldatabase-triggersql-function

解决方案

  group =(SELECT * FROM groups WHERE id=NEW.group_id);
  classe =(SELECT * FROM groups WHERE id=NEW.clazz_id);
  class_group =(SELECT * FROM groups WHERE id=classe.group_id);

这些子查询返回所有列 (SELECT *)。要正确填充变量，请选择行而不展开：group := (SELECT groups FROM groups WHERE ...)或执行 SELECT INTO：SELECT * INTO group FROM groups WHERE ...

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