The mi_qual_param_column() accessor function
The mi_qual_param_column() function retrieves the column number in the virtual table that is associated with the specified parameter.
Syntax
mi_smallint mi_qual_param_column(MI_AM_PARAM_DESC *paramDesc);- paramDesc
- Points to the parameter descriptor.
Usage
A parameter identifies a column by
a number that locates the column in the row descriptor. The mi_qual_param_column() function
returns the number 0 for the first column specified
in the row descriptor and adds 1 for each subsequent
column.
For example, assume that the WHERE clause contains the
function equal(name,'harry') and that name is
the second column in the row. The mi_qual_param_column() function
returns the value 1.
The access method might
need to identify the column by name, for example, to assemble a query
for an external database manager. To retrieve the column name, pass
the return value of mi_qual_param_column() and
the row descriptor to the DataBlade®
API mi_column_name() function
as in the following example:
rowDesc = mi_tab_rowdesc(tableDesc);
colnum=mi_qual_param_column(paramDesc);
colname=mi_column_name(rowDesc,colnum);Return values
The integer identifies the column argument by its position in the virtual table.