The mi_qual_column() accessor function
The mi_qual_column() function identifies the key-column argument to a strategy function.
Syntax
mi_smallint mi_qual_column(MI_AM_QUAL_DESC *qualDesc);- qualDesc
- Points to the qualification descriptor.
Usage
A qualification identifies a column by a number that locates the column in the row descriptor. The mi_qual_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 the WHERE clause contains the function equal(name,'harry') and that name is the second column in the row. The mi_qual_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_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_column(qualDesc);
colname=mi_column_name(rowDesc,colnum);Return values
The integer identifies the column argument by its position in the table row.
Related topics
See the description of:
- DataBlade API row-descriptor accessor functions in the HCL Informix® DataBlade API Programmer's Guide