如何在mysql中为A（表）联合B（表）与C（表）相交写查询

Question

我试着这样做

select Barcode from ITList union select Barcode from Equipment_list
intersect select Barcode from Scanneditem

Answer 1

检查一下：

SELECT a.Barcode FROM Scanneditem AS a
JOIN (SELECT Barcode FROM ITList UNION SELECT Barcode FROM Equipment_list) AS b
ON a.Barcode=b.Barcode;

Answer 2

您可以使用“存在”

Select * from (select Barcode from ITList union select Barcode from   Equipment_list) as t 
where exists (select Barcode from Scanneditem where Scanneditem.Barcode = t.Barcode)

Answer 3

虽然MySQL中没有INTERSECT运算符，但您可以使用IN子句或EXISTS子句轻松模拟此类查询，具体取决于INTERSECT查询的复杂性。

请试试这个：

SELECT * FROM (SELECT Barcode FROM ITList UNION SELECT Barcode FROM Equipment_list) AS allbarcode 
WHERE allbarcode.Barcode IN (SELECT Barcode FROM Scanneditem)

您还可以使用EXISTS子句检查Naveen Goyal sql（下面的回复）。