Question

我正在做作业，目前我有3张桌子。

[veiculos]
-placa (PK)
-categoria
-categoria_valor
-cor
-ano

[infracao]
-placa (PK)
-codigo
-descricao
-valor
-umt
-data
-hora
-local

[proprietario]
-placa (PK)
-nome
-endereco

我必须执行SQL查询才能得出placa, nome, endereco, codigo, descricao, valor, umt, data, hora, local, categoria, categoria_valor, cor, ano

我正在使用这个：

SELECT placa, null AS nome, null AS endereco, codigo, descricao, data, hora, local, valor, umt FROM infracao WHERE (placa=[@PLACA]) 
UNION 
SELECT null AS placa, nome, endereco, null, null, null, null, null AS tipo, null, null  FROM proprietario WHERE (placa=[@PLACA])
UNION 
SELECT null, null, null, null, null, null, categoria AS tipo, categoria_valor, cor, ano FROM veiculos WHERE (placa=[@PLACA])

;

结果是混乱的，它必须返回单列但使用三列，如您在此处看到的：https://i.imgur.com/F1xp8x9.png

我该如何解决？你能帮助我吗？我正在使用MS Access 2013

谢谢。

Answer 1

使用子查询和max（）

   select
   max(placa) as laca,
   max(nome) as nome,
   max(endereco) as endereco,
   max(codigo) as codigo,
   max(descricao) as descricao,
   max(data) as data,
   max(hora) as hora,max(local) as local,max(valor) as valor,
   max(umt) as umt from

     (SELECT placa, null AS nome, null AS endereco, codigo, descricao, data, hora, local, valor, umt FROM infracao WHERE (placa=[@PLACA]) 
        UNION 
        SELECT null AS placa, nome, endereco, null, null, null, null, null AS tipo, null, null  FROM proprietario WHERE (placa=[@PLACA])
        UNION 
        SELECT null, null, null, null, null, null, categoria AS tipo, categoria_valor, cor, ano FROM veiculos WHERE (placa=[@PLACA])
    ) a

多个UNION返回混乱的结果

1 个答案: