从 table1 中选择不在 table2 中的列

Posted 2023-05-09

【中文标题】从 table1 中选择不在 table2 中的列

【英文标题】：Select column from table1 which is not in table2

【发布时间】：2020-04-22 03:38:26

【问题描述】：

我有两张桌子

table1
=======================================
tid    subcategory     category
---------------------------------------
1      SUBCATEGORY1    CATEGORY1
2      SUBCATEGORY1    CATEGORY2
3      SUBCATEGORY2    CATEGORY1
4      SUBCATEGORY3    CATEGORY1
5      SUBCATEGORY4    CATEGORY1
6      SUBCATEGORY5    CATEGORY1
7      SUBCATEGORY6    CATEGORY1
8      SUBCATEGORY7    CATEGORY1
9      SUBCATEGORY8    CATEGORY1
10     SUBCATEGORY9    CATEGORY1


table2
=======================================
t2id   subcategory     category  pid
---------------------------------------
1      SUBCATEGORY1    CATEGORY1  1
2      SUBCATEGORY1    CATEGORY2  1
3      SUBCATEGORY2    CATEGORY1  1

我尝试显示table1中不在table2中的所有行，结果应该是这样的...

=======================================
tid    subcategory     category
---------------------------------------
4      SUBCATEGORY3    CATEGORY1
5      SUBCATEGORY4    CATEGORY1
6      SUBCATEGORY5    CATEGORY1
7      SUBCATEGORY6    CATEGORY1
8      SUBCATEGORY7    CATEGORY1
9      SUBCATEGORY8    CATEGORY1
10     SUBCATEGORY9    CATEGORY1

我正在使用这个查询...

select tl.* from table1 tl where subcategory and category not in(SELECT tl.subcategory, tl.category  FROM table1 as tl join table2 as bm where bm.pid='1' and tl.subcategory=bm.subcategory and tl.category=bm.category);

但它不起作用请帮助...

【参考方案1】：

我会在这里使用存在逻辑：

SELECT t1.tid, t1.subcategory, t1.category
FROM table1 t1
WHERE NOT EXISTS (SELECT 1 FROM table2 t2
                  WHERE t2.pim = 1 AND
                        t2.subcategory = t1.subcategory AND t2.category = t1.category);

【讨论】：

你能告诉我SELECT 1是什么意思

SELECT 1 只会返回一个记录，其中包含一个值为 1 的列，但这里的逻辑是检查 WHERE 子句中的条件是否存在。有关语法的更多信息，请阅读存在。