CODEWITHSUNDEEP
mysqlms-accessodbcdriver
zam911
zam911

Reputation: 13

Error running SQL in MS-Access with ODBC connection to MYSQL

I was helping a non-profit migrate MS-Access data to MYSQL. So, I ported data to MYSQL and created links in ms-access to MYSQL tables using ODBC. Majority of the existing SQL works fine. However I am stumped on this one error -

You have an error in your SQL syntax check the manual that corresponds to your MySQL server version for the right syntax to use near UNION...

I have stripped the SQL with 7 UNIONS to bare bones where it still fails.

(SELECT 1 as A FROM Households H)
UNION ALL
(SELECT 2 as A FROM Households H)
UNION ALL
(SELECT 3 as A FROM Households H)

The part that is getting to me is that I am able to run above successfully as long as I run only one UNION meaning below SQL, but the moment I add a third one, it gives ODBC error

(SELECT 1 as A FROM Households H)
UNION ALL
(SELECT 2 as A FROM Households H)

I tried using ` or ' or [] but none of these helped. The reason I am frustrated with this error is that either it should fail with all or none, it gives an error only when using two or more UNION clauses. Could this be a potential bug in driver?

I am using mysql-64 bit on win-7 64bit with ms-access and a 32-bit driver. It shouldn't be an architecture problem as I am able to run other queries with multiple UNIONs, and accessing the same set of tables.

It would be great if someone can give pointers on how to debug this further.

Upvotes: 1

Views: 2761

Answers (3)

Voitcus
Voitcus

Reputation: 4446

I am not sure about where the problem lies, but I think (though it's only an assumption) that this is on MS Access side. I had two UNION queries, each of them was putting some other queries together. Both used somewhat complicated sub-queries so I had lots of problem to create a pass-through query and I didn't want to use MySQL "views".

Surprisingly one of my queries worked, the other showed an error. My idea is that the working query used some Access features while the other was some kind of SELECT ... FROM's .

I don't know the rules but I think that when your query is simple, Access sends it to external database engine and puts one more bracket and causes an error. If you do a comlicated query, Access gets all data it needs and makes all necessary operations itself. For example, you may try to create a pivot query, that uses MSSQL TRANSFORM statement, which does not exist in MySQL, so it is obvious that Access handles it itself. So why couldn't it make SELECT by itself? I don't know. Maybe some performance reasons?

My working query differed from the other that it had one more (string) field that was calculated by built-in Access function. It used also Access & operator, which has another meaning (logical AND) in MySQL. (By the way to join strings in MySQL use CONCAT function). They of course need to be evaluated by Access, because MySQL does not understand this method of joining strings together.

I suggest just to make UNION not from tables, but from queries (like SELECT * FROM tablename and nothing more) and giving them a field that you don't need but that will force Access to handle the query. So a query (in Access) should look like this:

SELECT tablename.*, [somefield1]&[somefield2] AS useless_field FROM tablename;

(in my Access 2000 operations like "a" & "b" or IIf(true;true;false) were probably simplified and solved, so it didn't work. I think one needs at least one dynamic field to evaluate. I also did no performance tests. Probably it would be fastest if you add to integers, maybe just increase your index by 1?).

Then, of course, you join it together:

SELECT * FROM query1
UNION ALL
SELECT * FROM query2
UNION ALL
SELECT * FROM query3
UNION ALL

...

SELECT * FROM queryn
;

You don't need this useless_field of course.

I agree that this is a workaround but I have no other ideas.

Upvotes: 0

david
david

Reputation: 2638

It is a known MySQL problem: more than two UNION SELECT statement problem (with MS Access) but I don't know if the problem is in the MSAccess SQL parser (which compiles to ODBC SQL), or in the MySQL ODBC driver (which compiles ODBC SQL to MySQL SQL)

To work it out, I'd have to look at the ODBC log, and the ODBC specification, and see if Access was emmitting valid ODBC SQL.

That would be a waste of effort, since it makes more sense to use a pass-through query anyway. The main reason for using a native MSAccess query in this place would be to join to different data sources - for example, an Excel Spreadsheet and a MySQL table -, and according to the comments on the MySQL bug report, the problem goes away when you do that.

Upvotes: 1

user645280
user645280

Reputation:

In my version of Access, when I edit a query in Design (SQL) view there are three buttons at the top. "Union", "Pass-Through", and "Data Definition".

If I click "Pass-Through" your query works. If I click "Union" it breaks. Can you get away with using "Pass-Through" for this query?

Even in "Union" or "Data Definition" mode, this seems to work:

(SELECT 1, column1 as A FROM Households H)
UNION ALL
(SELECT 2, column2 as A FROM Households H)
UNION ALL
(SELECT 3, column3 as A FROM Households H);

Maybe Access is confused by only a single column?

Alternatively, just use a a multiplex table instead of a union:

SELECT mux.id,
IIf(mux.id=1,column1,IIf(mux.id=2,column2,column3)) AS A
FROM Households, mux;

Note: mux table should have 3 values in it 1,2,3. If it has more, you'd want to limit to the first 3 (or n) in a where clause.

Upvotes: 1

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