Error Code: 1222. The used SELECT statements have a different number of columns

Question

I\'v tried a few statements including joins, but have not been able to insert data from three other MySQL tables into one. On my last attempt, I received this error: Error Code:

Answer 1

The SELECT statement before the UNION keyword selects 4 columns but the SELECT statement after the UNION keyword selects only 1 column. You cannot build a UNION with different number of columns, thats the reason you get this error message about "different number of columns".