FORMULA LANGUAGE


@DbColumn (ODBC data source)
Example

Uses data source information to activate the appropriate ODBC driver. The driver then locates the specified DBMS, table, and column, and returns all values in that column. You can optionally specify whether the returned list of values is sorted, whether duplicate values are deleted, and how null values are handled.

Note @DbColumn can only retrieve data; it can't add, delete, or modify data.

Syntax

@DbColumn( "ODBC" : cache ; data_source ; user_ID1 : user_ID2 ; password1 : password2 ; table ; column : null_handling ; "Distinct" : sort )

Parameters

"ODBC"


cache data_source
user_ID1 : user_ID2
password1 : password2
table
column
null_handling
"Distinct"
sort
Return value

valuesFound


Note If you use the option button or the check box user interface for a keywords field, Lotus Domino updates the keyword list only when the document is composed or is loaded for editing. If you use the Standard user interface for the list, the keyword list is updated every time the document is recalculated.

Specifying the data source

The data source name can contain up to 32 alphanumeric characters.

@DbLookup can access data sources that have already been registered in the ODBC.INI file (or similar registry on platforms other than Windows™).

Specifying IDs and passwords

You only need these arguments if your DBMS requires them.

Instead of storing the IDs in the @DbColumn formula, you can replace them with null strings (""). If an ID is required, the user will be prompted for it. This is useful when you do not want other designers to see IDs, or when you want users to enter their own IDs when accessing external data. However, you must include IDs and passwords in formulas that run automatically (such as an agent) because these formulas don't prompt for information.

The user IDs and passwords for accessing a data source are required only once per Domino database session, as long as that database remains open. If the user opens another Domino database and executes a formula that accesses the same data source, the user ID and password will be required again.

Password parameters are necessary only when ID parameters are specified. Like IDs, passwords can either be stored in the @DbColumn formula, or prompted for by substituting the null string. If the database password is null, you can omit it from the formula.

For example, for the full ID/password specification, enter:


Specifying the table name

You can optionally include the name of the table's owner to remove ambiguity; use the format "owner_name.table_name", with a period to separate the owner name from the table name. For example:

"dbo.author"

Table can also refer to a database view in the DBMS being accessed.

Specifying null handling

Normally, null values are ignored and the resulting list is shortened (same as using the Discard option described below).

To control how null values are handled, specify one of the following, appended to the column parameter with a colon:


Specifying Distinct

The Distinct string argument is similar to @Unique in Lotus Domino, except that Distinct ensures that duplicate values are removed before the data is returned. Using Distinct instead of @Unique has two advantages:


Note Distinct is not supported by all ODBC drivers. If there are null values in the data and you specify Distinct, one null is usually returned.

Specifying sort

If you use the Distinct string argument, you can append the sort parameter to it with a colon. Use one of these keywords for the sort parameter to specify sorting of the return values:


If no sort string argument is specified, values are returned in arbitrary order.

Note The sort keywords are not supported by all ODBC drivers. If you attempt to use both Ascending and Descending in your formula, you see an "Invalid argument" message.

If multiple values are returned, they are formatted as a list and are separated with the multi-value separator designated for the current field.

@DbColumn can return no more than 64KB of data. Use the following equations to determine how much of your data can be returned with @DbColumn.


If the user's NOTES.INI file includes the statement

NoExternalApps=1

the @DbColumn formula is disabled. The user will not see an error message; the formula fails to execute. This applies to @DbColumn only when you use it with ODBC.

Usage

@DbColumn is intended mainly for keyword formulas. Instead of hard-coding a list of keywords and then periodically updating that list, @DbColumn allows you to dynamically retrieve a list of values from an external database table.

This function only works in Web applications if the remote server hosting the table from which data is being retrieved exists on the same machine as the Domino server, which is rarely the case.

Language cross-reference

GetValue method of Lotus Connectors ODBCResultSet class

Example
See Also