Parameter and Rowset Metadata
This topic provides information about the following type and type members, related to the OLE DB date and time enhancements.
DBBINDING structure
ICommandWithParameters::GetParameterInfo
ICommandWithParameters::SetParameterInfo
IColumnsRowset::GetColumnsRowset
IColumnsInfo::GetColumnInfo
ICommandWithParameters::GetParameterInfo
The following information is returned in the DBPARAMINFO structure through prgParamInfo:
Parameter Type |
wType |
ulParamSize |
bPrecision |
bScale |
dwFlags DBPARAMFLAGS_SS_ISVARIABLESCALE |
|---|---|---|---|---|---|
date |
DBTYPE_DBDATE |
6 |
10 |
0 |
Clear |
time |
DBTYPE_DBTIME2 |
10 |
8, 10..16 |
0..7 |
Set |
smalldatetime |
DBTYPE_DBTIMESTAMP |
16 |
16 |
0 |
Clear |
datetime |
DBTYPE_DBTIMESTAMP |
16 |
23 |
3 |
Clear |
datetime2 |
DBTYPE_DBTIMESTAMP |
16 |
19,21..27 |
0..7 |
Set |
datetimeoffset |
DBTYPE_DBTIMESTAMPOFFSET |
20 |
26,28..34 |
0..7 |
Set |
Notice that in some cases value ranges are not continuous. This is due to the addition of a decimal point when fractional precision is greater than zero.
DBPARAMFLAGS_SS_ISVARIABLESCALE is only valid when connected to a SQL Server 2008 (or later) server. DBPARAMFLAGS_SS_ISVARIABLESCALE is never set when connected to down-level servers.
ICommandWithParameters::SetParameterInfo and Implied Parameter Types
The information provided in the DBPARAMBINDINFO structure must conform to the following:
pwszDataSourceType (provider specific) |
pwszDataSourceType (OLE DB generic) |
ulParamSize |
bScale |
|---|---|---|---|
|
DBTYPE_DATE |
6 |
Ignored |
date |
DBTYPE_DBDATE |
6 |
Ignored |
|
DBTYPE_DBTIME |
10 |
Ignored |
time |
DBTYPE_DBTIME2 |
10 |
0..7 |
smalldatetime |
|
16 |
Ignored |
datetime |
|
16 |
Ignored |
datetime2 or DBTYPE_DBTIMESTAMP |
DBTYPE_DBTIMESTAMP |
16 |
0..7 |
datetimeoffset |
DBTYPE_DBTIMESTAMPOFFSET |
20 |
0..7 |
The bPrecision parameter is ignored.
"DBPARAMFLAGS_SS_ISVARIABLESCALE" is ignored when sending data to the server. Applications can force the use of legacy tabular-data stream (TDS) types by using the provider-specific type names "datetime" and "smalldatetime". When connected to SQL Server 2008 (or later) servers, "datetime2" format will be used and an implicit server conversion will occur, if necessary, when the type name is "datetime2" or "DBTYPE_DBTIMESTAMP". bScale is ignored if the provider specific type names "datetime" or "smalldatetime" are used. Otherwise, appications must ensure that bScale is set correctly. Applications upgraded from MDAC and SQL Server Native Client from SQL Server 2005 that use "DBTYPE_DBTIMESTAMP" will fail if they do not set bScale correctly. When connected to server instances earlier than SQL Server 2008, a bScale value other than 0 or 3 with "DBTYPE_DBTIMESTAMP" is an error and E_FAIL will be returned.
When ICommandWithParameters::SetParameterInfo is not called, the provider imples the server type from the binding type as specified in IAccessor::CreateAccessor as follows:
Binding Type |
pwszDataSourceType (provider specific) |
|---|---|
DBTYPE_DATE |
datetime2(0) |
DBTYPE_DBDATE |
date |
DBTYPE_DBTIME |
time(0) |
DBTYPE_DBTIME2 |
time(7) |
DBTYPE_DBTIMESTAMP |
datetime2(7) |
DBTYPE_DBTIMESTAMPOFFSET |
datetimeoffset(7) |
IColumnsRowset::GetColumnsRowset
IColumnsRowset::GetColumnsRowset returns the following columns:
Column Type |
DBCOLUMN_TYPE |
DBCOLUM_COLUMNSIZE |
DBCOLUMN_PRECISION |
DBCOLUMN_SCALE, DBCOLUMN_DATETIMEPRECISION |
DBCOLUMN_FLAGS, DBCOLUMNFLAGS_SS_ISVARIABLESCALE |
|---|---|---|---|---|---|
date |
DBTYPE_DBDATE |
6 |
10 |
0 |
Clear |
time |
DBTYPE_DBTIME2 |
10 |
8, 10..16 |
0..7 |
Set |
smalldatetime |
DBTYPE_DBTIMESTAMP |
16 |
16 |
0 |
Clear |
datetime |
DBTYPE_DBTIMESTAMP |
16 |
23 |
3 |
Clear |
datetime2 |
DBTYPE_DBTIMESTAMP |
16 |
19, 21..27 |
0..7 |
Set |
datetimeoffset |
DBTYPE_DBTIMESTAMPOFFSET |
20 |
26, 28..34 |
0..7 |
Set |
In DBCOLUMN_FLAGS, DBCOLUMNFLAGS_ISFIXEDLENGTH is always true for date/time types and the following flags are always false:
DBCOLUMNFLAGS_CACHEDEFERRED
DBCOLUMNFLAGS_ISBOOKMARK
DBCOLUMNFLAGS_ISCHAPTER
DBCOLUMNFLAGS_ISLONG
DBCOLUMNFLAGS_ISROWID
DBCOLUMNFLAGS_ISROWVER
DBCOLUMNFLAGS_MAYDEFER
The remaining flags (DBCOLUMNFLAGS_ISNULLABLE, DBCOLUMNFLAGS_MAYBENULL, DBCOLUMNFLAGS_WRITE, and DBCOLUMNFLAGS_WRITEUNKNOWN) can be set, depending on how the column is defined and the actual query.
A new flag DBCOLUMNFLAGS_SS_ISVARIABLESCALE is provided in DBCOLUMN_FLAGS to allow an application to determine the server type of columns, where DBCOLUMN_TYPE is DBTYPE_DBTIMESTAMP. DBCOLUMN_SCALE or DBCOLUMN_DATETIMEPRECISION must also be used to identify the server type.
DBCOLUMNFLAGS_SS_ISVARIABLESCALE is only valid when connected to a SQL Server 2008 (or later) server. DBCOLUMNFLAGS_SS_ISVARIABLESCALE is undefined when connected to down-level servers.
IColumnsInfo::GetColumnInfo
DBCOLUMNINFO structure returns the following information:
Parameter Type |
wType |
ulColumnSize |
bPrecision |
bScale |
dwFlags DBPARAMFLAGS_SS_ISVARIABLESCALE |
|---|---|---|---|---|---|
date |
DBTYPE_DBDATE |
6 |
10 |
0 |
Clear |
time(1..7) |
DBTYPE_DBTIME2 |
10 |
8, 10..16 |
0..7 |
Set |
smalldatetime |
DBTYPE_DBTIMESTAMP |
16 |
16 |
0 |
Clear |
datetime |
DBTYPE_DBTIMESTAMP |
16 |
23 |
3 |
Clear |
datetime2 |
DBTYPE_DBTIMESTAMP |
16 |
19, 21..27 |
0..7 |
Set |
datetimeoffset |
DBTYPE_DBTIMESTAMPOFFSET |
20 |
26, 28..34 |
0..7 |
Set |
In dwFlags, DBCOLUMNFLAGS_ISFIXEDLENGTH is always true for date/time types and the following flags are always false:
DBCOLUMNFLAGS_CACHEDEFERRED
DBCOLUMNFLAGS_ISBOOKMARK
DBCOLUMNFLAGS_ISCHAPTER
DBCOLUMNFLAGS_ISLONG
DBCOLUMNFLAGS_ISROWID
DBCOLUMNFLAGS_ISROWVER, MAYDEFER
The remaining flags (DBCOLUMNFLAGS_ISNULLABLE, DBCOLUMNFLAGS_MAYBENULL, DBCOLUMNFLAGS_WRITE, and DBCOLUMNFLAGS_WRITEUNKNOWN) can be set.
A new flag DBCOLUMNFLAGS_SS_ISVARIABLESCALE is provided in dwFlags to allow an application to determine the server type of columns, where wType is DBTYPE_DBTIMESTAMP. bScale must also be used to identify the server type.