如何连接列不为null的表

Question

我正在尝试将两个表中的数据连接到USSN不为空的表中;

在没有添加“WHERE CONTACT2.USSN IS NOT NULL”的情况下，它完美运行。没有运气，我尝试了不同的排列。

SELECT B.CONTACT,
       B.LASTNAME,
       B.PHONE1,
       B.PHONE2,
       B.PHONE3,
       A.ACCOUNTNO,
       A.USCOREEFX,
       A.USCORETUC,
       A.USCOREXPN,
       A.USCORE1EFX,
       A.USCORE1TUC,
       A.USCORE1XPN
FROM CONTACT2 A
INNER JOIN CONTACT1 B
ON A.ACCOUNTNO = B.ACCOUNTNO
WHERE USSN IS NOT NULL

Answer 1

我明白了。

SELECT B.CONTACT,
       B.LASTNAME,
       B.PHONE1,
       B.PHONE2,
       B.PHONE3,
       A.ACCOUNTNO,
       A.USCOREEFX,
       A.USCORETUC,
       A.USCOREXPN,
       A.USCORE1EFX,
       A.USCORE1TUC,
       A.USCORE1XPN
FROM CONTACT2 A
INNER JOIN CONTACT1 B
ON A.ACCOUNTNO = B.ACCOUNTNO
WHERE A.USSN IS NOT NULL