带有联合和两个内部联接的假列？

Question

我有这个查询：

SELECT * FROM (
(SELECT ACCOUNTS.INSTALLTIME, ACCOUNTS.HONAME, ACCOUNTS.ADDRESS, ACCOUNTS.CITY, ACCOUNTS.STATE, ACCOUNTS.ZIP, ACCOUNTS.JOBNUMBER, ACCOUNTS.INSTALLDATE, ACCOUNTS.RESULT, ACCOUNTS.NOTES, ACCOUNTS.SMNOTES, technicians.technumber, technicians.boardplacing 
FROM ACCOUNTS 
INNER JOIN technicians ON ACCOUNTS.INSTALLER = technicians.technumber) 
UNION 
(SELECT service.servicetime, service.Customername, service.address, service.city, service.state, service.zip, service.ID, service.serviceday, service.result, service.servicenotes, service.board, technicians.technumber, technicians.boardplacing
FROM service 
INNER JOIN technicians ON service.technician= technicians.technumber)
) as t WHERE t.INSTALLDATE = '$date' ORDER BY t.boardplacing

有什么方法可以进行类似于以下的查询：

SELECT * FROM (
(SELECT ACCOUNTS.INSTALLTIME, ACCOUNTS.HONAME, ACCOUNTS.ADDRESS, ACCOUNTS.CITY, ACCOUNTS.STATE, ACCOUNTS.ZIP, ACCOUNTS.JOBNUMBER, ACCOUNTS.INSTALLDATE, ACCOUNTS.RESULT, ACCOUNTS.NOTES, ACCOUNTS.SMNOTES, '' as priority, ACCOUNTS.PAFS, ACCOUNTS.upsell, ACCOUNTS.TERM, ACCOUNTS.MMRUPGRADE, ACCOUNTS.WARRANTY, ACCOUNTS.EFT, technicians.technumber, technicians.boardplacing 
FROM ACCOUNTS 
INNER JOIN technicians ON ACCOUNTS.INSTALLER = technicians.technumber) 
UNION 
(SELECT service.servicetime, service.Customername, service.address, service.city, service.state, service.zip, service.ID, service.serviceday, service.result, service.servicenotes, service.board, '', '', '', '', '', '', technicians.technumber, technicians.boardplacing
FROM service 
INNER JOIN technicians ON service.technician= technicians.technumber)
) as t WHERE t.INSTALLDATE = '$date' ORDER BY t.boardplacing

基本上我的工会需要假专栏。有什么办法可以通过连接来实现这一点吗？还有其他更好的方法吗？

Answer 1

当我编写联合查询并需要“假”或“虚拟”列时，我只需使用：

NULL AS Fake

所以整个查询看起来像这样；

SELECT A.CHEESE, A.BREAD, A.GARLIC, A.COST
FROM ACHEESETABLE A
WHERE A.BREAD = WHEAT

UNION ALL

SELECT NULL AS CHEESE, B.BREAD, NULL AS GARLIC, B.COST
FROM BCHEESYTABLE B
WHERE B.COST > 15 

这样两个查询都有CHEESEandGARLIC列，但BCHEESYTABLE不包含CHEESEor列GARLIC。这样做还允许WHERE两个查询使用不同的条件，因此本质上可以在同一查询中拥有两个不同的记录群体。