mysql选择优先级的值

Question

我有一个包含数千个数据的表位置

我的SQL查询是

select * 
from location_table 
where country = "PH" 
and (province = "NCR" OR province = "") 
and (city = "makati" or city="") limit 10

location_table

ID | country | province | city
1  |   PH    |    NCR   | makati
2  |   PH    |    NCR   | makati
3  |   PH    |    NCR   | makati
4  |   PH    |    NCR   | makati
5  |   PH    |    NCR   | marikina
6  |   PH    |    NCR   | 
7  |   PH    |          | 
8  |   US    |          | 

这是正确的。这是否可以确保我的输出将是这样的

ID | country | province | city
1  |   PH    |    NCR   | makati
2  |   PH    |    NCR   | makati
3  |   PH    |    NCR   | makati
4  |   PH    |    NCR   | makati
6  |   PH    |    NCR   | 
7  |   PH    |          | 

我需要确保我的查询是准确的。我需要改进我的查询吗？我需要优先考虑城市和省的价值。如果它有一个省。或者获取与城市相同的null值。

例如，

city = makati 我需要优先考虑所有城市的“makati”价值。如果在ID 3000上怎么办？那里有一个makati。我需要首先使用makati获取所有城市，而不是使用null值的城市。与省相同。

Answer 1

使用ORDER BY将非空值放在第一位：

select * 
from location_table 
where country = "PH" 
and (province = "NCR" OR province = "") 
and (city = "makati" or city="")
order by province = "", city = ""

当列为空时，

columnname = ""将为1，否则为0。

DEMO

Answer 2

select * 
from location_table 
where country = "PH" 
and (province = "NCR" OR province = "") 
and (city = "makati" or city="")
order by province, city

Order By将解决您的问题。

Answer 3

要检查null，请始终使用＆＃39;为空＆＃39;条款。 find_in_set也可以帮到你