Para armazenar o horário normal de operação, você precisa armazenar vários registros contendo:
- Loja - INTEIRO
- DiaDaSemana - INTEIRO (0-6)
- OpenTime - TIME
- FecharHora - HORA
Suponho, por exemplo, que cada loja tenha reduzido o horário durante os feriados nacionais ou tenha paradas de fábrica, então você também precisaria armazenar alguns registros de substituição:
- Loja - INTEIRO
- SubstituirDataInício - DATA
- OverrideEndDate - DATE
- DiaDaSemana - INTEIRO (0-6)
- AltOpenTime - TIME
- AltCloseTime - TIME
- Fechado - INTEIRO (0, 1)
Encontrar lojas abertas é trivial, mas você também precisa verificar se há horários de substituição:
SELECT Shop
FROM OverrideHours
WHERE OverrideStartDate <= NOW()
AND OverrideEndDate >= NOW()
AND DayOfWeek = WEEKDAY(NOW())
Se houver algum registro devolvido, essas lojas têm horário alternado ou estão fechadas.
Pode haver algum bom SQL-fu que você possa fazer aqui, mas isso lhe dá o básico.
EDITAR
Eu não testei isso, mas isso deve chegar perto:
SELECT Normal.Shop
FROM Normal
LEFT JOIN Override
ON Normal.Shop = Override.Shop
AND Normal.DayOfWeek = Override.DayOfWeek
AND NOW() BETWEEN Override.OverrideStartDate AND Override.OverrideEndDate
WHERE Normal.DayOfWeek = WEEKDAY(NOW())
AND ((Override.Shop IS NULL AND TIME(NOW()) BETWEEN Normal.OpenTime AND Normal.CloseTime)
OR (Override.Shop IS NOT NULL AND Override.Closed <> 1 AND TIME(NOW()) BETWEEN Override.AltOpenTime AND Override.AltCloseTime))
EDITAR
Quanto à eficiência, é eficiente no sentido de que você só precisa fazer uma chamada para o MySQL, o que geralmente é um gargalo se estiver em uma rede. Você terá que testar e ver se isso funciona de acordo com suas especificações. Se não, você pode jogar com alguns índices.
EDITAR
Teste. Não testes completos, mas alguns.
mysql> select * from Normal;
+------+-----------+----------+-----------+
| Shop | DayOfWeek | OpenTime | CloseTime |
+------+-----------+----------+-----------+
| 1 | 1 | 09:00:00 | 17:00:00 |
| 1 | 5 | 09:00:00 | 16:00:00 |
| 2 | 1 | 09:00:00 | 17:00:00 |
| 2 | 5 | 09:00:00 | 17:00:00 |
+------+-----------+----------+-----------+
4 rows in set (0.01 sec)
mysql> select * from Override;
+------+-------------------+-----------------+-----------+-------------+--------------+--------+
| Shop | OverrideStartDate | OverrideEndDate | DayOfWeek | AltOpenTime | AltCloseTime | Closed |
+------+-------------------+-----------------+-----------+-------------+--------------+--------+
| 2 | 2010-12-01 | 2010-12-31 | 1 | 09:00:00 | 18:00:00 | 0 |
| 2 | 2010-12-01 | 2010-12-31 | 5 | 09:00:00 | 18:00:00 | 0 |
| 1 | 2010-12-01 | 2010-12-31 | 1 | 09:00:00 | 17:00:00 | 1 |
+------+-------------------+-----------------+-----------+-------------+--------------+--------+
3 rows in set (0.00 sec)
mysql> SET @whenever = TIMESTAMP('2010-11-23 16:05');
Query OK, 0 rows affected (0.00 sec)
mysql> SELECT WEEKDAY(@whenever);
+--------------------+
| WEEKDAY(@whenever) |
+--------------------+
| 1 |
+--------------------+
1 row in set (0.00 sec)
mysql> SELECT Normal.Shop FROM Normal LEFT JOIN Override ON Normal.Shop = Override.Shop AND Normal.DayOfWeek = Override.DayOfWeek AND @whenever BETWEEN Override.OverrideStartDate AND Override.OverrideEndDate WHERE Normal.DayOfWeek = WEEKDAY(@whenever) AND ((Override.Shop IS NULL AND TIME(@whenever) BETWEEN Normal.OpenTime AND Normal.CloseTime) OR (Override.Shop IS NOT NULL AND Override.Closed <> 1 AND TIME(@whenever) BETWEEN Override.AltOpenTime AND Override.AltCloseTime));
+------+
| Shop |
+------+
| 1 |
| 2 |
+------+
2 rows in set (0.00 sec)
mysql> SET @whenever = TIMESTAMP('2010-11-23 17:05');
Query OK, 0 rows affected (0.00 sec)
mysql> SELECT Normal.Shop FROM Normal LEFT JOIN Override ON Normal.Shop = Override.Shop AND Normal.DayOfWeek = Override.DayOfWeek AND @whenever BETWEEN Override.OverrideStartDate AND Override.OverrideEndDate WHERE Normal.DayOfWeek = WEEKDAY(@whenever) AND ((Override.Shop IS NULL AND TIME(@whenever) BETWEEN Normal.OpenTime AND Normal.CloseTime) OR (Override.Shop IS NOT NULL AND Override.Closed <> 1 AND TIME(@whenever) BETWEEN Override.AltOpenTime AND Override.AltCloseTime));
Empty set (0.01 sec)
mysql> SET @whenever = TIMESTAMP('2010-12-25 16:05');
Query OK, 0 rows affected (0.00 sec)
mysql> SELECT Normal.Shop FROM Normal LEFT JOIN Override ON Normal.Shop = Override.Shop AND Normal.DayOfWeek = Override.DayOfWeek AND @whenever BETWEEN Override.OverrideStartDate AND Override.OverrideEndDate WHERE Normal.DayOfWeek = WEEKDAY(@whenever) AND ((Override.Shop IS NULL AND TIME(@whenever) BETWEEN Normal.OpenTime AND Normal.CloseTime) OR (Override.Shop IS NOT NULL AND Override.Closed <> 1 AND TIME(@whenever) BETWEEN Override.AltOpenTime AND Override.AltCloseTime));
+------+
| Shop |
+------+
| 2 |
+------+
1 row in set (0.00 sec)
mysql> SET @whenever = TIMESTAMP('2010-11-23 17:05');
Query OK, 0 rows affected (0.00 sec)
mysql> SELECT WEEKDAY(@whenever);
+--------------------+
| WEEKDAY(@whenever) |
+--------------------+
| 1 |
+--------------------+
1 row in set (0.00 sec)
mysql> SELECT Normal.Shop FROM Normal LEFT JOIN Override ON Normal.Shop = Override.Shop AND Normal.DayOfWeek = Override.DayOfWeek AND @whenever BETWEEN Override.OverrideStartDate AND Override.OverrideEndDate WHERE Normal.DayOfWeek = WEEKDAY(@whenever) AND ((Override.Shop IS NULL AND TIME(@whenever) BETWEEN Normal.OpenTime AND Normal.CloseTime) OR (Override.Shop IS NOT NULL AND Override.Closed <> 1 AND TIME(@whenever) BETWEEN Override.AltOpenTime AND Override.AltCloseTime));
Empty set (0.00 sec)
