The mi_column_id() function
The mi_column_id() function obtains the column identifier of a specified column from a row descriptor.
Syntax
mi_integer mi_column_id(row_desc, colname)
MI_ROW_DESC *row_desc;
mi_string *colname;- row_desc
- A pointer to the row descriptor for the row that contains the specified column.
- colname
- A pointer to a null-terminated string to contain the column name.
| Valid in client LIBMI application? | Valid in user-defined routine? |
|---|---|
| Yes | Yes |
Usage
A row descriptor can describe the
structure of a row in a table or the structure of a row type. From
the row descriptor that row_desc references, the mi_column_id() function
obtains a column identifier for either structure:
- The column identifier of the colname column in the row
- The column identifier of the colname field for the row type
A column identifier is the position of the column or field
within the row descriptor. Column numbering follows C array-indexing
conventions: the first column in the row is at position zero.
Tip: The system catalog tables refer to the unique number that
identifies a column definition as its column identifier.
However, the DataBlade®
API refers
to this number as a column number and the position of
a column within the row structure as a column identifier.
These two terms do not refer to the same value.
For more information about row descriptors, see the Informix® DataBlade® API Programmer's Guide.
Return values
- >=0
- The column position of the specified column or field in the specified row descriptor.
- MI_ERROR
- The function was not successful.