Error 1222 (21000): The used SELECT statements have a different number of columns

这个错误是由于你的子查询返回的列数不一致导致的。根据你的代码，第一个子查询返回了5列（id、created_at、schedule、content、url），而第二个子查询只返回了3列（id、created_at、content）。由于 UNION 操作要求两个子查询返回的列数必须一致，所以会报错。

为了解决这个问题，你可以在两个子查询中添加相应的空值列来使它们的列数一致。例如，你可以在第二个子查询中添加一个空值列来与第一个子查询的 "schedule" 列对应：

common.DB.Raw("SELECT id, created_at, schedule, content, url FROM records WHERE pm_id = ? AND status = 2 AND deleted_at IS NULL "+
			"UNION "+
			"SELECT id, created_at, NULL AS schedule, content, NULL AS url FROM supervisings WHERE pm_id = ? AND deleted_at IS NULL")
			.Scan(&count)

通过在第二个子查询中添加了空值列，使得两个子查询返回的列数保持一致，从而避免了错误。请根据你的具体需求和数据模型进行相应的调整。

相关问题

go:257 Error 1222 (21000): The used SELECT statements have a different number of columns

这个错误是因为你在使用 UNION 操作符时，SELECT 语句的列数不一致导致的。请确保所有 SELECT 语句的列数相同，或者使用 NULL 填充缺少的列。例如：

SELECT column1, column2, null as column3 FROM table1
UNION
SELECT column1, null as column2, column3 FROM table2

这样就可以保证两个 SELECT 语句的列数相同了。希望能帮到你！

The used SELECT statements have a different number of columns

This error usually occurs when you are trying to combine two or more SELECT statements with a UNION operator, but the columns in each SELECT statement do not match. To fix this error, you need to make sure that the number of columns and their data types are the same in all the SELECT statements.

For example, if you have two SELECT statements like this:

SELECT name, age FROM users;
SELECT email, phone FROM contacts;

You cannot combine them using a UNION operator because they have different columns. Instead, you need to modify them to have the same number of columns:

SELECT name, age, NULL AS email, NULL AS phone FROM users;
SELECT NULL AS name, NULL AS age, email, phone FROM contacts;

In this modified version, both SELECT statements have four columns, with two columns set to NULL in each statement. Now you can combine them using a UNION operator:

SELECT name, age, email, phone
FROM (
  SELECT name, age, NULL AS email, NULL AS phone FROM users
  UNION
  SELECT NULL AS name, NULL AS age, email, phone FROM contacts
) AS combined;

This will give you a result set with four columns: name, age, email, and phone, where some of the columns may have NULL values.