Applications need to determine the number of items in a result set and the format of each item before they can bind items and fetch rows.
Applications that process the results of known queries have this information already, but applications that process the results of ad hoc queries do not.
To handle the results of an ad hoc query, the application must:
Determine the number of result columns.
Determine the name, datatype, length, and so forth of each column.
In DB-Library, an application calls different routines to obtain the number of items in a result set, depending on the type of results being retrieved.
In Client-Library, whenever the ct_results result_type parameter indicates fetchable data, the application can retrieve the number of data items by calling ct_res_info(CS_NUMDATA).
Table 5-12 lists DB-Library routines that ct_res_info(CS_NUMDATA) replaces:
Routine |
Description |
|---|---|
dbnumalts |
Returns the number of columns in a compute row |
dbnumcols |
Determines the number of regular columns for the current set of results |
dbnumrets |
Determines the number of return parameter values generated by a stored procedure |
A DB-Library application calls several routines to get a description of a data item.
A Client-Library application calls ct_describe once to initialize a CS_DATAFMT structure that completely describes any data value.
Table 5-13 lists DB-Library routines that ct_describe replaces:
DB-Library routine |
Value returned |
CS_DATAFMT field (set by ct_describe) |
|---|---|---|
dbaltlen |
The maximum length of data for a particular compute column |
maxlength |
dbcollen |
The maximum length of data for a particular regular result column |
maxlength |
dbretlen |
The length of a stored procedure return parameter value |
maxlength |
dbalttype |
The datatype of a compute column |
datatype |
dbcoltype |
The datatype of a regular result column |
datatype |
dbrettype |
The datatype of a stored procedure return parameter value |
datatype |
dbaltutype |
The user-defined datatype for a compute column |
usertype |
dbcolutype |
The user-defined datatype for a regular result column |
usertype |
dbcolname |
The name of a regular result column |
name |
dbretname |
The name of a stored procedure parameter for a particular return parameter value |
name |
dbdatlen |
The actual length of a regular result column value |
None. This information is returned using ct_bind’s copied parameter or ct_get_data’s outlen parameter. |
dbadlen |
The actual length of a compute column value |
|
dbretlen |
The actual length of a return parameter value |
