在mysql中创建带有联合的视图，但所有记录都显示在1列下

Question

I'm trying to create a view in MYSQL but when using Union ALL it is being shown underneath 1 column. when I try to add column names it simply says that the amount of columns and results dont match

use TestDB;
DROP VIEW if exists auditTableView;
Create view auditTableView
AS
select usernames.username from usernames LEFT JOIN auditTable on usernames.ID = auditTable.userID
Union ALL

select actionDesc.functionName from actionDesc LEFT JOIN auditTable on actionDesc.actionID = auditTable.actionID
Union all

SELECT timestamp from auditTable;


SELECT * FROM auditTableView;

Answer 1

From what can be gathered of your schema, it looks like you want to do an inner join from the auditTable to your usernames and actionDesc table, and select the username, actionDesc, and timestamp values from there:

use TestDB;
DROP VIEW if exists auditTableView;
Create view auditTableView
AS

select
    usernames.username,
    actionDesc.functionName,
    auditTable.timestamp
from auditTable
    inner join usernames
        on usernames.ID = auditTable.userID
    inner join actionDesc
        on actionDesc.actionID = auditTable.actionID;

select * from auditTableView;

Answer 2

With UNION , MySQL uses the column names from the first SELECT statement, and the number of columns must match.

You can do something like this:

SELECT table1.col1, NULL AS col2 FROM table1
UNION ALL
SELECT NULL AS col1, table2.col2 FROM table2