在多个数据库上的单个MySQL查询

Question

I am working with the following set-up:

Consider two MySQL databases: abc and xyz , each with their own table: abc . table_in_abc and xyz . table_in_xyz . I need to run a simple MySQL query that select elements from the table_in_abc with a JOIN relationship to table_in_xyz .

In Workbench, the following query works fine:

SELECT AB.* , XY.*
FROM `abc`.`table_in_abc` AB
LEFT JOIN `xyz`.`table_in_xyz` XY ON AB.`ID` = XY`ID`

I am trying to achieve the same things in VBA. I am able to run a MySQL query on a single database (see example below) but unable to do so when the query involves multiple databases.

Example of simple VBA query on single database:

Set conn = New ADODB.Connection
conn.Open "DRIVER={MySQL ODBC 5.3 Unicode Driver}" _
& ";SERVER=" & server_name _
& ";DATABASE=" & database_name _
& ";UID=" & user_id _
& ";PWD=" & password _
& ";OPTION=3" '

Set rs1 = New ADODB.Recordset
sqlstr = "SELECT * FROM `abc`.`table_in_abc` WHERE `ID`=" & ID & ";" 
rs1.Open sqlstr, conn, adOpenStatic
With Worksheets("Main").Cells(a, 1)
.ClearContents
.CopyFromRecordset rs1
End With
rs1.Close
Set rs1 = Nothing

Answer 1

I found a way to solve my above problem by simply setting two connections to the two different databases (working on the same MySQL instance).

My code looks like that :

Set conn = New ADODB.Connection
conn.Open "DRIVER={MySQL ODBC 5.3 Unicode Driver}" _
& ";SERVER=" & server_name _
& ";DATABASE=" & database_name _
& ";UID=" & user_id _
& ";PWD=" & password _
& ";OPTION=3" '

Set conn2 = New ADODB.Connection
conn2.Open "DRIVER={MySQL ODBC 5.3 Unicode Driver}" _
& ";SERVER=" & server_name _
& ";DATABASE=" & database_name2 _
& ";UID=" & user_id2 _
& ";PWD=" & password2 _
& ";OPTION=3" '

' SELECT Query with LEFT JOIN on the two different databases
Set rs1 = New ADODB.Recordset
sqlstr = "SELECT AB.* , XY.* FROM `abc`.`table_in_abc` AB LEFT JOIN `xyz`.`table_in_xyz` XY ON AB.`ID` = XY`ID`"
rs1.Open sqlstr, conn, adOpenStatic
With Worksheets("main").Cells(1, 1)
.ClearContents
.CopyFromRecordset rs1
End With
rs1.Close
Set rs1 = Nothing