Question

如何组合以下SQL查询，以便在同一行的3个单独列中获得一个包含州，城市和邮政编码名称的输出表？我对SQL没有什么经验，但是如果我能做一个单独的查询，那对我来说似乎好一点。

SELECT City_tx FROM City WHERE City_id = 11

SELECT StateProv_tx FROM StateProv WHERE StateProv_id = 12

SELECT PostalCode_tx FROM PostalCode WHERE PostalCode_id = 13

Answer 1

如果表之间没有任何关系。只需声明3个变量＆amp;设置它们（只是除上述答案之外的另一种方法）;

DECLARE @City VARCHAR(100), @StateProv VARCHAR(100), @PostalCode VARCHAR(100)

SELECT @City = City_tx FROM City WHERE City_id = 11
SELECT @StateProv = StateProv_tx FROM StateProv WHERE StateProv_id = 12
SELECT @PostalCode = PostalCode_tx FROM PostalCode WHERE PostalCode_id = 13

SELECT @City City, @StateProv StateProv, @PostalCode PostalCode

Answer 2

select max(City_tx),max(StateProv_tx),max(PostalCode_tx) from
(
SELECT City_tx ,'' StateProv_tx, '' PostalCode_tx FROM City WHERE City_id = 11
union all
SELECT '' City_tx ,StateProv_tx, '' PostalCode_tx  FROM StateProv WHERE StateProv_id = 12
union all
SELECT '' City_tx ,'' StateProv_tx, PostalCode_tx FROM PostalCode WHERE PostalCode_id = 13
) t

Answer 3

假设City_id，StateProv_id和PostalCode_id都是唯一的，那么只需使用交叉连接并仅限制这些字段。如果你在其他数据之间没有其他关系，那么可能不是最有效的，但不是任何其他好的选择：

SELECT City_tx, StateProv_tx, PostalCode_tx
FROM City, StateProv, PostalCode
WHERE City_id = 11 AND StateProv_id = 12 AND PostalCode_id = 13

尽管如此，除非我们没有架构或有关数据如何布局的任何信息，否则这可能无法为您工作。

Answer 4

SELECT City_tx, (SELECT StateProv_tx FROM StateProv WHERE StateProv_id = 12) as sp_tx, (SELECT PostalCode_tx FROM PostalCode WHERE PostalCode_id = 13) as pc_tx FROM City WHERE City_id = 11

它应该有效......至少在MySQL中。

Answer 5

Cross join似乎是一种很好的方法，假设在每种情况下只返回一行：

select *
from (SELECT City_tx FROM City WHERE City_id = 11) c cross join
     (SELECT StateProv_tx FROM StateProv WHERE StateProv_id = 12) s cross join
     (SELECT PostalCode_tx FROM PostalCode WHERE PostalCode_id = 13) p

结合SQL查询？

5 个答案: