mysql except用不了

MySQL 中没有 `EXCEPT` 关键字，但是可以使用 `NOT IN` 或 `LEFT JOIN` 来实现类似的功能。以下是使用 `NOT IN` 实现 `EXCEPT` 的示例：

假设有两个表 A 和 B，需要从 A 中排除 B 中存在的数据，可以使用以下 SQL 语句：

SELECT * FROM A WHERE A.id NOT IN (SELECT id FROM B);

这将返回 A 表中存在但是 B 表中不存在的数据。

另外，使用 `LEFT JOIN` 也可以实现类似的功能，具体可以参考以下 SQL 语句：

SELECT A.* FROM A LEFT JOIN B ON A.id = B.id WHERE B.id IS NULL;

这将返回 A 表中存在但是 B 表中不存在的数据。

相关问题

mysql except关键字用不了

MySQL中没有`EXCEPT`关键字，但可以使用`NOT IN`或`LEFT JOIN`和`NULL`来实现类似的功能。例如，以下查询将返回`table1`中有但`table2`中没有的行：

SELECT column1, column2, ...
FROM table1
WHERE column1 NOT IN (SELECT column1 FROM table2);

或者使用`LEFT JOIN`和`NULL`：

SELECT table1.column1, table1.column2, ...
FROM table1
LEFT JOIN table2 ON table1.column1 = table2.column1
WHERE table2.column1 IS NULL;

mysql except

MySQL does not have an `EXCEPT` operator like some other database management systems (DBMS). However, you can achieve similar functionality using other techniques. One common approach is to use the `NOT IN` operator or the `LEFT JOIN` clause.

Here's an example that demonstrates how you can perform an `EXCEPT` operation in MySQL using `NOT IN`:

SELECT column_name
FROM table1
WHERE column_name NOT IN (SELECT column_name FROM table2);

In this example, `table1` and `table2` are the tables you want to compare, and `column_name` is the column you want to use for comparison.

Alternatively, you can use a `LEFT JOIN` to achieve the same result:

SELECT t1.column_name
FROM table1 t1
LEFT JOIN table2 t2 ON t1.column_name = t2.column_name
WHERE t2.column_name IS NULL;

Here, you left join `table1` with `table2` on the column you want to compare, and then filter out the rows where the column value in `table2` is null.

These techniques allow you to emulate the functionality of the `EXCEPT` operator in MySQL.