KB178717 - INF: Excel ODBC Driver and Text ODBC Driver Notes

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Reading:
To use the ODBC catalog functions, an Excel table must have data in it.

The Excel driver supports Excel versions 3.0, 4.0, 5.0/7.0, and 97. Column names, if present, must be in the first row. Excel 3.0, 5.0, and 97 file formats must have a database range defined.
Writing:
When creating a table, the driver will create:
- A 3.0 version if the version of the data source through which the connection was made is "Excel" (that is, Excel 3.0/4.0).
- A worksheet in the workbook to which it is connected if the version of the data source was "Excel 5.0/7.0" or "Excel 97".
Concurrency:
By default, all tables are opened read-only. The user must explicitly choose to open exclusively by clicking to clear the Read Only check box in Excel Setup.
Maximum column name length:
Column names over 64 characters will produce an error.
Delimited column names:
The Excel driver will allow column names to contain any valid Excel characters, including spaces. Delimited Identifiers will have to be used in this case. Do not use an exclamation point character (!) in a column name, because it has a special meaning in Excel; if a column name contains an exclamation point, the Excel IISAM will internally convert it to a dollar sign ($) character.
Driver-generated column names:
Unspecified (blank) column names will be replaced with driver-generated names (for example, Col1 for column 1, and so on).

Inserting into table:
Applications that want to use the Save As option for Excel data would issue a CREATE TABLE statement for the new table and then do subsequent INSERT operations into the new table. INSERT statements result in an append to the table. No other operations can be done on the table until it is closed and reopened the first time. After the table is closed the first time, no subsequent inserts can be done.
Unsupported SQL:
The driver will not support DELETE, UPDATE, or ALTER TABLE statements. While it is possible to update values, DELETE statements will not remove a row from a table based on an Excel spreadsheet. These operations are not supported. Basically, you can only append (insert) to a table.
Treatment of zero-length strings:
Because the underlying data format doesn't have any way to differentiate between an empty string and NULL data, a query with a search condition containing an empty string will not match any empty strings in the table. This is because the empty string is treated as a NULL in this case, and NULL never matches anything (not even another NULL).

No HTML support
Unsupported SQL:
The driver does not support DELETE, UPDATE, CREATE INDEX, DROP INDEX, or ALTER TABLE statements.
Maximum length of a text column recognized by "Guess":
The Guess functionality of the Text driver only works on Text columns that are less than 64,513 bytes.
Treatment of zero-length strings:
Because the underlying data format doesn't have any way to differentiate between an empty string and NULL data, a query with a search condition containing an empty string will not match any empty strings in the table. This is because the empty string is treated as a NULL in this case, and NULL never matches anything (not even another NULL).