MySQL: Fatal error encountered during data read.

I got it here.

I solved my problems by creating the appended table in dax, not in power query, using union.

I think the fact that in desktop it works, and in service it doesn't, is that when you append a table in power query, m language goes around the fact that the tables havn't the same number of columns, by creating new ones on the table that has less. It also append by column name, so the columns doesn't have to be in the same order.

When it goes to the service, it converts the append into a sql union function, and then the error "MySQL: Fatal error encountered during data read" comes.

When I first tried to use the union function in dax, it return an error, about the number of columns of the 2 tables. After that the issue was that the data went to the wrong columns, even when the order was the same in power query. Turns out, the order of the columns is the order of creation of each one.

So I used SELECTCOLUMNS and fixed all the problems.

Appended Table = 

UNION( 

    SELECTCOLUMNS(
	Table1,
        "Name 1", Table1[Column 1],
        "Name 2", Table1[Column 2],
        "Name 3", Table1[Column 3]
    ),

    SELECTCOLUMNS(
	Table2,
        "Name 1", Table2[Column 1],
        "Name 2", Table2[Column 2],
        "Name 3", Table2[Column 3]
    )
)​