DatabaseLookup
Name | DatabaseLookup | |
---|---|---|
Purpose | Looks up a value in a database. | |
Description | The DatabaseLookup function returns a single value of the
specified column that satisfies the specified condition. Only certain functions are translated into SQL for
evaluation by the database and can be used with DatabaseColumn and DatabaseFunction functions. These are:
You can also use any function as part of the expression tree to reference elements from your map. You just can't have the DatabaseColumn or DatabaseFunction be a child of functions other than on the list above. |
|
Data type returned | Depends on the database column specified | |
Properties | Output Column | The fully qualified column whose value is to be returned by this function. The specification is of the form: <path to database>.<table>.<column> for example: /Default Project/Databases/MyDatabase.MYTABLE.MYCOLUMN. Note that when using the Studio a graphical interface specifies this, so you don't need to be concerned with this format. |
Caching | Specifies if the values returned by this function are
cached. Possible values are:
|
|
Arguments | Condition (Boolean) | The "where" condition for this lookup. This is an expression that includes DatabaseColumn (and maybe DatabaseFunction) functions to specify to the database the selection criteria for the lookup. Use the normal functions for specifying conditions (e.g. Equal, And, Add). These functions will be translated into the corresponding SQL for evaluation by the database. You may use any other type of function in the Condition as well to refer to elements in the map for example. |
Output Column (String) | The output column to select. This is mainly used when you want to use a function with the output column. For example, selecting the maximum value of a column. Use a DatabaseFunction to specify the function and a single DatabaseColumn within that to specify the column. |