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Limitations

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This section describes limitations of the ODBC Desktop Database Drivers regarding the following sections:

Function limitations

Function Limitations
Aggregate functions An aggregate function and a non-aggregate column reference can't both be used as arguments to a single SQL statement.
Scalar functions Scalar functions are supported only by using the ODBC canonical format.
Set functions The set functions (AVG, MAX, MIN, and SUM) don't support the DISTINCT keyword.
Sorting The maximum length of a sort key in a GROUP BY clause, ORDER BY clause, SELECT DISTINCT statement, or outer join is 255 bytes; the maximum length of all sort keys in a sort row is 65,500 bytes.
CONVERT Type conversion failures result in the affected column being set to NULL.

DATE and TIMESTAMP data type can't be converted to another data type (or itself) by the CONVERT function.

Statement limitations

Statement Limitations
ALTER TABLE For more information, see ALTER TABLE statement limitations.
CALL Expressions aren't supported as parameters to a called procedure (applies to Microsoft Access driver).
CREATE INDEX For more information, see CREATE INDEX statement limitations.
CREATE TABLE For more information, see CREATE TABLE statement limitations.
DELETE For more information, see DELETE statement limitations.
DROP INDEX The DROP INDEX statement isn't supported (applies to Microsoft Excel or Text drivers).
DROP TABLE When the Microsoft Excel 5.0, 7.0, or 97 driver is used, the DROP TABLE statement clears the worksheet but doesn't delete the worksheet name. Because the worksheet name still exists in the workbook, another worksheet can't be created with the same name.
INSERT For more information, see INSERT statement limitations.
SELECT DISTINCT The DISTINCT keyword doesn't apply to binary data.
SELECT For more information, see SELECT statement limitations.
UPDATE For more information, see UPDATE statement limitations.

Clauses, types, and other limitations

Clause or type Limitations
Column names For more information, see Column name limitations.
Data types For more information, see Data type limitations.
Date arithmetic Date arithmetic isn't supported for subtracting a DATE data type from a DATE data type.
Identifiers For more information, see Identifiers limitations.
Index name When the Paradox driver is used, a primary index must have the same name as the table upon which it's defined. Other unique or non-unique indexes must have the same name as the table upon which they're defined.
Parameterized query When the Microsoft Access driver is used, a parameterized query can be called using the following syntax: CALL query-name [ ( parameter [ , parameter ] ... ) ].
Reserved keywords For more information, see Reserved keyword limitations.
AND predicate A maximum of 40 is supported.
DISTINCT keyword Not supported for Long Text fields (Microsoft Access) or Memo fields (dBASE).
FROM clause The maximum number of tables in a FROM clause is 16.
HAVING clause The maximum number of search conditions in a HAVING clause is 40.
LIKE predicate For more information, see LIKE predicate limitations.
NOT NULL The NOT NULL`` constraint in the CREATE TABLE statement isn't supported.
ORDER BY clause If a SELECT statement contains a GROUP BY clause and an ORDER BY clause, the ORDER BY clause can contain only a column in the result set or an expression in the GROUP BY clause.
Table names For more information, see Table name limitations.
Table references A maximum of 16 table references can be included in any query statement.
Views Not supported by the dBASE, Microsoft Excel, Paradox, or Text drivers.
WHERE clause The maximum number of clauses in a WHERE clause is 40.

LONGVARBINARY and LONGVARCHAR columns can be compared to literals of up to 255 characters in length, but can't be compared using parameters.
WHERE CURRENT OF clause Not supported.
Strings For more information, see String limitations.