OVERLAPS 运算符检查多个行

Question

目前我正在使用重叠运算符，这样用户就无法插入重叠的日期。我创建了这个函数：

    CREATE OR REPLACE FUNCTION overlap(docent_medewerkerscode1 CHARACTER(7),  
lokaal1 TEXT, groep_groepsnaam1 TEXT, startdatum1 timestamp, einddatum1 
timestamp)

RETURNS TEXT AS $$
DECLARE
    resultaat TEXT;
    rec rooster%rowtype;
BEGIN 
    FOR rec IN SELECT groep_groepsnaam = groep_groepsnaam1 OR lokaal =      
lokaal1 OR docent_medewerkerscode = docent_medewerkerscode1 FROM rooster 
  LOOP
        IF(startdatum1, einddatum1) OVERLAPS (startdatum, einddatum) FROM  
rooster THEN
           --IF startdatum1 BETWEEN startdatum AND einddatum AND einddatum1 BETWEEN startdatum AND einddatum FROM rooster THEN
            resultaat = 'tijd overlapt';
            RAISE 'Niet mogelijk tijd komt overeen met ingeplande tijd';
        END IF;
  END LOOP;

RETURN resultaat;
END;
$$ LANGUAGE plpgsql;

问题是重叠不适用于多行。

(ERROR: query "SELECT (startdatum1, einddatum1) OVERLAPS (startdatum, einddatum) FROM rooster" returned more than one row)

我正在寻找一种方法，让重叠检查 select 查询中的每一行。你们中有人知道我能做什么吗？

Answer 1

错误消息的直接原因是 plpgsql IF statement 需要一个单个布尔表达式，而您的代码 returns 一整套布尔表达式.

IF(startdatum1, einddatum1) OVERLAPS (startdatum, einddatum) FROM  
rooster THEN

是以下的丑陋缩写形式：

IF (SELECT(startdatum1, einddatum1) OVERLAPS (startdatum, einddatum)
    FROM  rooster) THEN

而且这种方式根本无效。您必须汇总或使用 EXISTS:

IF EXISTS (
   SELECT 1 FROM  rooster r
   WHERE  (startdatum1, einddatum1) OVERLAPS (r.startdatum, r.einddatum)
   ) THEN ...

更重要的是，exclusion constraint 几乎肯定是您问题的更好解决方案（需要 Postgres 9.0+）：

Postgres constraint for unique datetime range
Preventing adjacent/overlapping entries with EXCLUDE in PostgreSQL

OVERLAPS 运算符检查多个行

OVERLAPS operator to check multiples rows

postgresql

database-design

plpgsql

overlap