我对选择两个表并以格式显示结果有疑问。假设表是;
表1;
+-----+-----------+
| Ref | MaterialX |
+-----+-----------+
| 1 | mmm |
| 1 | nnn |
| 1 | kkk |
+-----+-----------+
表2;
+-----+-----------+
| Ref | MaterialY |
+-----+-----------+
| 1 | aaa |
| 1 | bbb |
+-----+-----------+
伪查询是;选择两个表并根据ref字段合并结果(ref和material字段不是主键,Thoose只是关系第三个表(
结果(我想要(;
+-----+-----------+-----------+
| Ref | MaterialX | MaterialY |
+-----+-----------+-----------+
| 1 | mmm | NULL |
| 1 | nnn | NULL |
| 1 | kkk | NULL |
| 1 | NULL | aaa |
| 1 | NULL | bbb |
+-----+-----------+-----------+
有办法吗?
您可以使用简单的并集,因为这两个表是不相关的。
SELECT ref, materialX, null as MaterialY from table_1
union all
SELECT ref, null as materialX, MaterialY from table_2