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SQLFetch
Conformance
Version Introduced: ODBC 1.0
Standards Compliance: ISO 92
Summary
SQLFetch fetches the next rowset of data from the result set and returns data for all
bound columns.
Syntax
SQLRETURN SQLFetch(
SQLHSTMT StatementHandle);
Arguments
StatementHandle [Input]
Statement handle.
Returns
SQL_SUCCESS, SQL_SUCCESS_WITH_INFO, SQL_NO_DATA, SQL_STILL_EXECUTING,
SQL_ERROR, or SQL_INVALID_HANDLE.
Diagnostics
When SQLFetch returns either SQL_ERROR or SQL_SUCCESS_WITH_INFO, an associated SQLSTATE
value can be obtained by calling SQLGetDiagRec with a HandleType of SQL_HANDLE_STMT and a Handle of StatementHandle. The following table lists the SQLSTATE values commonly returned by SQLFetch and explains each one in the context of this function; the notation “(DM)”
precedes the descriptions of SQLSTATEs returned by the Driver Manager. The return
code associated with each SQLSTATE value is SQL_ERROR, unless noted otherwise.
If an error occurs on a single column, SQLGetDiagField can be called with a DiagIdentifier of SQL_DIAG_COLUMN_NUMBER to determine the column the error occurred on; and SQLGetDiagField can be called with a DiagIdentifier of SQL_DIAG_ROW_NUMBER to determine the row containing that column.
For all those SQLSTATEs that can return SQL_SUCCESS_WITH_INFO or SQL_ERROR
(except 01xxx SQLSTATEs), SQL_SUCCESS_WITH_INFO is returned if an error occurs on
one or more, but not all, rows of a multirow operation, and SQL_ERROR is
returned if an error occurs on a single-row operation.
SQLSTATE
| Error
| Description
|
01000
| General warning
| Driver-specific informational message. (Function returns
SQL_SUCCESS_WITH_INFO.)
|
01004
| String data, right truncated
| String or binary data returned for a column resulted in the truncation of
non-blank character or non-NULL binary data. If it was a string value, it was right
truncated.
|
01S01
| Error in row
| An error occurred while fetching one or more rows.
(If this SQLSTATE is returned when an ODBC 3.0 application is working with an
ODBC 2.x driver, it can be ignored.)
|
01S07
| Fractional truncation
| The data returned for a column was truncated. For numeric data types, the
fractional part of the number was truncated. For time, timestamp, and interval data
types containing a time component, the fractional portion of the time was
truncated.
|
07006
| Restricted data type attribute violation
| The data value of a column in the result set could not be converted to the
data type specified by TargetType in SQLBindCol.
Column 0 was bound with a data type of SQL_C_BOOKMARK and the
SQL_ATTR_USE_BOOKMARKS statement attribute was set to SQL_UB_VARIABLE.
Column 0 was bound with a data type of SQL_C_VARBOOKMARK and the
SQL_ATTR_USE_BOOKMARKS statement attribute was not set to SQL_UB_VARIABLE.
|
07009
| Invalid descriptor index
| The driver was an ODBC 2.x driver that does not support SQLExtendedFetch, and a column number specified in the binding for a column was 0.
Column 0 was bound and the SQL_ATTR_USE_BOOKMARKS statement attribute was set
to SQL_UB_OFF.
|
08S01
| Communication link failure
| The communication link between the driver and the data source to which the
driver was connected failed before the function completed processing.
|
22001
| String data, right truncated
| A variable-length bookmark returned for a column was truncated.
|
22002
| Indicator variable required but not supplied
| NULL data was fetched into a column whose StrLen_or_IndPtr set by SQLBindCol (or SQL_DESC_INDICATOR_PTR set by SQLSetDescField or SQLSetDescRec) was a null pointer.
|
22003
| Numeric value out of range
| Returning the numeric value (as numeric or string) for one or more bound
columns would have caused the whole (as opposed to fractional) part of the number to
be truncated.
For more information, see “Converting Data from SQL to C Data Types” in Appendix D, “Data Types.”
|
22007
| Invalid datetime format
| A character column in the result set was bound to a date, time, or timestamp C
structure, and a value in the column was, respectively, an invalid date, time,
or timestamp.
|
22012
| Division by zero
| A value from an arithmetic expression was returned which resulted in division
by zero.
|
22015
| Interval field overflow
| Assigning from an exact numeric or interval SQL type to an interval C type
caused a loss of significant digits in the leading field.
When fetching data to an interval C type, there was no representation of the
value of the SQL type in the interval C type.
|
22018
| Invalid character value for cast specification
| A character column in the result set was bound to a character C buffer and the
column contained a character for which there was no representation in the
character set of the buffer.
The C type was an exact or approximate numeric, a datetime, or an interval
data type; the SQL type of the column was a character data type; and the value in
the column was not a valid literal of the bound C type.
|
24000
| Invalid cursor state
| The StatementHandle was in an executed state but no result set was associated with the StatementHandle.
|
40001
| Serialization failure
| The transaction in which the fetch was executed was terminated to prevent
deadlock.
|
40003
| Statement completion unknown
| The associated connection failed during the execution of this function and the
state of the transaction cannot be determined.
|
HY000
| General error
| An error occurred for which there was no specific SQLSTATE and for which no
implementation-specific SQLSTATE was defined. The error message returned by SQLGetDiagRec in the *MessageText buffer describes the error and its cause.
|
HY001
| Memory allocation error
| The driver was unable to allocate memory required to support execution or
completion of the function.
|
HY008
| Operation canceled
| Asynchronous processing was enabled for the StatementHandle. The function was called and before it completed execution, SQLCancel was called on the StatementHandle. Then the function was called again on the StatementHandle.
The function was called and, before it completed execution, SQLCancel was called on the StatementHandle from a different thread in a multithread application.
|
HY010
| Function sequence error
| (DM) The specified StatementHandle was not in an executed state. The function was called without first calling SQLExecDirect, SQLExecute, or a catalog function.
(DM) An asynchronously executing function (not this one) was called for the StatementHandle and was still executing when this function was called.
(DM) SQLExecute, SQLExecDirect, SQLBulkOperations, or SQLSetPos was called for the StatementHandle and returned SQL_NEED_DATA. This function was called before data was sent for
all data-at-execution parameters or columns.
(DM) SQLFetch was called for the StatementHandle after SQLExtendedFetch was called and before SQLFreeStmt with the SQL_CLOSE option was called.
|
HY013
| Memory management error
| The function call could not be processed because the underlying memory objects
could not be accessed, possibly because of low memory conditions.
|
HY090
| Invalid string or buffer length
| The SQL_ATTR_USE_BOOKMARK statement attribute was set to SQL_UB_VARIABLE, and
column 0 was bound to a buffer whose length was not equal to the maximum length
for the bookmark for this result set. (This length is available in the
SQL_DESC_OCTET_LENGTH field of the IRD, and can be obtained by calling SQLDescribeCol, SQLColAttribute, or SQLGetDescField.)
|
HY107
| Row value out of range
| The value specified with the SQL_ATTR_CURSOR_TYPE statement attribute was
SQL_CURSOR_KEYSET_DRIVEN, but the value specified with the SQL_ATTR_KEYSET_SIZE
statement attribute was greater than 0 and less than the value specified with the
SQL_ATTR_ROW_ARRAY_SIZE statement attribute.
|
HYC00
| Optional feature not implemented
| The driver or data source does not support the conversion specified by the
combination of the TargetType in SQLBindCol and the SQL data type of the corresponding column.
|
HYT01
| Connection timeout expired
| The connection timeout period expired before the data source responded to the
request. The connection timeout period is set through SQLSetConnectAttr, SQL_ATTR_CONNECTION_TIMEOUT.
|
IM001
| Driver does not support this function
| (DM) The driver associated with the StatementHandle does not support the function.
|
Comments
SQLFetch returns the next rowset in the result set. It can be called only while a
result set exists—that is, after a call that creates a result set and before the
cursor over that result set is closed. If any columns are bound, it returns the
data in those columns. If the application has specified a pointer to a row
status array or a buffer in which to return the number of rows fetched, SQLFetch returns this information as well. Calls to SQLFetch can be mixed with calls to SQLFetchScroll but cannot be mixed with calls to SQLExtendedFetch. For more information, see “Fetching a Row of Data” in Chapter 10, “Retrieving Results (Basic).”
If an ODBC 3.0 application works with an ODBC 2.x driver, the Driver Manager maps SQLFetch calls to SQLExtendedFetch for an ODBC 2.x driver that supports SQLExtendedFetch. If the ODBC 2.x driver does not support SQLExtendedFetch, the Driver Manager maps SQLFetch calls to SQLFetch in the ODBC 2.x driver, which can only fetch a single row.
For more information, see “Block Cursors, Scrollable Cursors, and Backward Compatibility” in Appendix G, “Driver Guidelines for Backward Compatibility.”
Positioning the Cursor
When the result set is created, the cursor is positioned before the start of
the result set. SQLFetch fetches the next rowset. It is equivalent to calling SQLFetchScroll with FetchOrientation set to SQL_FETCH_NEXT. For more information about cursors, see “Cursors” in Chapter 10, “Retrieving Results (Basic)” and “Block Cursors” in Chapter 11, “Retrieving Results (Advanced).”
The SQL_ATTR_ROW_ARRAY_SIZE statement attribute specifies the number of rows
in the rowset. If the rowset being fetched by SQLFetch overlaps the end of the result set, SQLFetch returns a partial rowset. That is, if S + R–1 is greater than L, where S is
the starting row of the rowset being fetched, R is the rowset size, and L is the
last row in the result set, then only the first L–S+1 rows of the rowset are
valid. The remaining rows are empty and have a status of SQL_ROW_NOROW.
After SQLFetch returns, the current rowis the first row of the rowset.
The following rules describe cursor positioning after a call to SQLFetch:
Condition
| First row of new rowset
|
Before start
| 1
|
CurrRowsetStart <= LastResultRow – RowsetSize [1]
| CurrRowsetStart + RowsetSize [2]
|
CurrRowsetStart > LastResultRow – RowsetSize [1]
| After end
|
After end
| After end
|
where:
Before start
| The block cursor is positioned before the start of the result set. If the
first row of the new rowset is before the start of the result set, SQLFetch returns SQL_NO_DATA.
|
After end
| The block cursor is positioned after the end of the result set. If the first
row of the new rowset is after the end of the result set, SQLFetch returns SQL_NO_DATA.
|
CurrRowsetStart
| The number of the first row in the current rowset.
|
LastResultRow
| The number of the last row in the result set.
|
RowsetSize
| The rowset size.
|
|
[1] If the rowset size is changed between fetches, this is the rowset size that
was used with the previous fetch.
[2] If the rowset size is changed between fetches, this is the rowset size that
was used with the new fetch.
|
For example, suppose a result set has 100 rows and the rowset size is 5. The
following table shows the rowset and return code returned by SQLFetch for different starting positions.
Current rowset
|
Return code
|
New rowset
| # of rows fetched
|
Before start
| SQL_SUCCESS
| 1 to 5
| 5
|
1 to 5
| SQL_SUCCESS
| 6 to 10
| 5
|
52 to 56
| SQL_SUCCESS
| 57 to 61
| 5
|
91 to 95
| SQL_SUCCESS
| 96 to 100
| 5
|
93 to 97
| SQL_SUCCESS
| 98 to 100. Rows 4 and 5
of the row status array
are set to
SQL_ROW_NOROW.
| 3
|
96 to 100
| SQL_NO_DATA
| None.
| 0
|
99 to 100
| SQL_NO_DATA
| None.
| 0
|
After end
| SQL_NO_DATA
| None.
| 0
|
Returning Data in Bound Columns
As SQLFetch returns each row, it places the data for each bound column in the buffer
bound to that column. If no columns are bound, SQLFetch does not return any data but does move the block cursor forward. The data can
still be retrieved with SQLGetData. If the cursor is a multirow cursor (that is, the SQL_ATTR_ROW_ARRAY_SIZE is
greater than 1), SQLGetData can be called only if SQL_GD_BLOCK is returned when SQLGetInfo is called with an InfoType of SQL_GETDATA_EXTENSIONS. (For more information, see SQLGetData.)
For each bound column in a row, SQLFetch does the following:
1 Sets the length/indicator buffer to SQL_NULL_DATA and proceeds to the next
column if the data is NULL. If the data is NULL and no length/indicator buffer was
bound, SQLFetch returns SQLSTATE 22002 (Indicator variable required but not supplied) for the
row and proceeds to the next row. For information about how to determine the
address of the length/indicator buffer, see “Buffer Addresses” in SQLBindCol.
If the data for the column is not NULL, SQLFetch proceeds to step 2.
2 If the SQL_ATTR_MAX_LENGTH statement attribute is set to a nonzero value and
the column contains character or binary data, the data is truncated to
SQL_ATTR_MAX_LENGTH bytes.
Note The SQL_ATTR_MAX_LENGTH statement attribute is intended to reduce network
traffic. It is generally implemented by the data source, which truncates the
data before returning it across the network. Drivers and data sources are not
required to support it. Therefore, to guarantee that data is truncated to a
particular size, an application should allocate a buffer of that size and specify the
size in the cbValueMax argument in SQLBindCol.
3 Converts the data to the type specified by TargetType in SQLBindCol.
4 If the data was converted to a variable-length data type, such as character or
binary, SQLFetch checks whether the length of the data exceeds the length of the data buffer.
If the length of character data (including the null-termination character)
exceeds the length of the data buffer, SQLFetch truncates the data to the length of the data buffer less the length of a
null-termination character. It then null-terminates the data. If the length of
binary data exceeds the length of the data buffer, SQLFetch truncates it to the length of the data buffer. The length of the data buffer
is specified with BufferLength in SQLBindCol.
SQLFetch never truncates data converted to fixed-length data types; it always assumes
that the length of the data buffer is the size of the data type.
5 Places the converted (and possibly truncated) data in the data buffer. For
information about how to determine the address of the data buffer, see “Buffer
Addresses” in SQLBindCol.
6 Places the length of the data in the length/indicator buffer. If the indicator
pointer and the length pointer were both set to the same buffer (as a call to SQLBindCol does), the length is written in the buffer for valid data and SQL_NULL_DATA
is written in the buffer for NULL data. If no length/indicator buffer was bound, SQLFetch does not return the length.
For character or binary data, this is the length of the data after conversion
and before truncation due to the data buffer being too small. If the driver
cannot determine the length of the data after conversion, as is sometimes the case
with long data, it sets the length to SQL_NO_TOTAL. If data was truncated due
to the SQL_ATTR_MAX_LENGTH statement attribute, the value of this attribute—as
opposed to the actual length—is placed in the length/indicator buffer. This is
because this attribute is designed to truncate data on the server before
conversion, so the driver has no way of figuring out what the actual length is.
For all other data types, this is the length of the data after conversion;
that is, it is the size of the type to which the data was converted.
For information about how to determine the address of the length/indicator
buffer, see “Buffer Addresses” in SQLBindCol.
7 If the data is truncated during conversion without a loss of significant
digits (for example, the real number 1.234 is truncated when converted to the
integer 1) and SQLFetch returns SQLSTATE 01S07 (Fractional truncation) and SQL_SUCCESS_WITH_INFO. If
the data is truncated because the length of the data buffer is too small (for
example, the string “abcdef” is placed in a 4-byte buffer), SQLFetch returns SQLSTATE 01004 (Data truncated) and SQL_SUCCESS_WITH_INFO. If data is
truncated due to the SQL_ATTR_MAX_LENGTH statement attribute, SQLFetch returns SQL_SUCCESS and does not return SQLSTATE 01S07 (Fractional
truncation) or SQLSTATE 01004 (Data truncated). If data is truncated during conversion
with a loss of significant digits (for example, if an SQL_INTEGER value greater
than 100,000 were converted to an SQL_C_TINYINT), SQLFetch returns SQLSTATE 22003 (Numeric value out of range) and SQL_ERROR (if the
rowset size is 1) or SQL_SUCCESS_WITH_INFO (if the rowset size is greater than 1).
The contents of the bound data buffer and the length/indicator buffer are
undefined if SQLFetch or SQLFetchScroll does not return SQL_SUCCESS or SQL_SUCCESS_WITH_INFO.
Row Status Array
The row status array is used to return the status of each row in the rowset.
The address of this array is specified with the SQL_ATTR_ROW_STATUS_PTR
statement attribute. The array is allocated by the application and must have as many
elements as are specified by the SQL_ATTR_ROW_ARRAY_SIZE statement attribute. Its
values are set by SQLFetch, SQLFetchScroll, and SQLBulkOperations or SQLSetPos (except when they have been called after the cursor has been positioned by SQLExtendedFetch). If the value of the SQL_ATTR_ROW_STATUS_PTR statement attribute is a null
pointer, these functions do not return the row status.
The contents of the row status array buffer are undefined if SQLFetch or SQLFetchScroll does not return SQL_SUCCESS or SQL_SUCCESS_WITH_INFO.
The following values are returned in the row status array.
Row status array value
| Description
|
SQL_ROW_SUCCESS
| The row was successfully fetched and has not changed since it was last fetched
from this result set.
|
SQL_ROW_SUCCESS_
WITH_INFO
| The row was successfully fetched and has not changed since it was last fetched
from this result set. However, a warning was returned about the row.
|
SQL_ROW_ERROR
| An error occurred while fetching the row.
|
SQL_ROW_UPDATED [1],[2],[3]
| The row was successfully fetched and has changed since it was last fetched
from this result set. If the row is fetched again from this result set, or is
refreshed by SQLSetPos, the status changed to the row’s new status.
|
SQL_ROW_DELETED [3]
| The row has been deleted since it was last fetched from this result set.
|
SQL_ROW_ADDED [4]
| The row was inserted by SQLBulkOperations. If the row is fetched again from this result set, or is refreshed by SQLSetPos, its status is SQL_ROW_SUCCESS.
|
SQL_ROW_NOROW
| The rowset overlapped the end of the result set and no row was returned that
corresponded to this element of the row status array.
|
|
[1] For keyset, mixed, and dynamic cursors, if a key value is updated, the row of
data is considered to have been deleted and a new row added.
[2] Some drivers cannot detect updates to data and therefore cannot return this
value. To determine whether a driver can detect updates to refetched rows, an
application calls SQLGetInfo with the SQL_ROW_UPDATES option.
[3] SQLFetch can return this value only when it is intermixed with calls to SQLFetchScroll. The reason for this is that SQLFetch moves forward through the result set and, when used exclusively, does not
refetch any rows. Because no rows are refetched, SQLFetch does not detect changes made to previously fetched rows. However, if SQLFetchScroll positions the cursor before any previously fetched rows and SQLFetch is used to fetch those rows, SQLFetch can detect any changes to those rows.
[4] Returned by SQLBulkOperations only. Not set by SQLFetch or SQLFetchScroll.
|
Rows Fetched Buffer
The rows fetched buffer is used to return the number of rows fetched,
including those rows for which no data was returned because an error occurred while
they were being fetched. In other words, it is the number of rows for which the
value in the row status array is not SQL_ROW_NOROW. The address of this buffer is
specified with the SQL_ATTR_ROWS_FETCHED_PTR statement attribute. The buffer
is allocated by the application. It is set by SQLFetch and SQLFetchScroll. If the value of the SQL_ATTR_ROWS_FETCHED_PTR statement attribute is a null
pointer, these functions do not return the number of rows fetched. To determine
the number of the current row in the result set, an application can call SQLGetStmtAttr with the SQL_ATTR_ROW_NUMBER attribute.
The contents of the rows fetched buffer are undefined if SQLFetch or SQLFetchScroll does not return SQL_SUCCESS or SQL_SUCCESS_WITH_INFO, except when SQL_NO_DATA
is returned, in which case the value in the rows fetched buffer is set to 0.
Error Handling
Errors and warnings can apply to individual rows or to the entire function.
For more information about diagnostic records, see Chapter 15, “Diagnostics,” and SQLGetDiagField.
Errors and Warnings on the Entire Function
If an error applies to the entire function, such as SQLSTATE HYT00 (Timeout
expired) or SQLSTATE 24000 (Invalid cursor state), SQLFetch returns SQL_ERROR and the applicable SQLSTATE. The contents of the rowset
buffers are undefined and the cursor position is unchanged.
If a warning applies to the entire function, SQLFetch returns SQL_SUCCESS_WITH_INFO and the applicable SQLSTATE. The status records
for warnings that apply to the entire function are returned before the status
records that apply to individual rows.
Errors and Warnings in Individual Rows
If an error (such as SQLSTATE 22012 (Division by zero)) or a warning (such as
SQLSTATE 01004 (Data truncated)) applies to a single row, SQLFetch:
Sets the corresponding element of the row status array to SQL_ROW_ERROR for
errors or SQL_ROW_SUCCESS_WITH_INFO for warnings.
Adds zero or more status records containing SQLSTATEs for the error or warning.
Sets the row and column number fields in the status records. If SQLFetch cannot determine a row or column number, it sets that number to
SQL_ROW_NUMBER_UNKNOWN or SQL_COLUMN_NUMBER_UNKNOWN respectively. If the status record does
not apply to a particular column, SQLFetch sets the column number to SQL_NO_COLUMN_NUMBER.
SQLFetch continues fetching rows until it has fetched all of the rows in the rowset.
It returns SQL_SUCCESS_WITH_INFO unless an error occurs in every row of the
rowset (not counting rows with status SQL_ROW_NOROW), in which case it returns
SQL_ERROR. In particular, if the rowset size is 1 and an error occurs in that row, SQLFetch returns SQL_ERROR.
SQLFetch returns the status records in row number order. That is, it returns all
status records for unknown rows (if any), then all status records for the first row
(if any), then all status records for the second row (if any), and so on. The
status records for each individual row are ordered according to the normal rules
for ordering status records; for more information, see “Sequence of Status
Records” in SQLGetDiagField.
Descriptors and SQLFetch
The following sections describe how SQLFetch interacts with descriptors.
Argument Mappings
The driver does not set any descriptor fields based on the arguments of SQLFetch.
Other Descriptor Fields
The following descriptor fields are used by SQLFetch.
Descriptor field
| Desc.
| Field in
| Set through
|
SQL_DESC_ARRAY_SIZE
| ARD
| header
| SQL_ATTR_ROW_ARRAY_SIZE statement attribute
|
SQL_DESC_ARRAY_STATUS_PTR
| IRD
| header
| SQL_ATTR_ROW_STATUS_PTR statement attribute
|
SQL_DESC_BIND_OFFSET_PTR
| ARD
| header
| SQL_ATTR_ROW_BIND_OFFSET_PTR statement attribute
|
SQL_DESC_BIND_TYPE
| ARD
| header
| SQL_ATTR_ROW_BIND_TYPE statement attribute
|
SQL_DESC_COUNT
| ARD
| header
| ColumnNumber argument of SQLBindCol
|
SQL_DESC_DATA_PTR
| ARD
| records
| TargetValuePtr argument of SQLBindCol
|
SQL_DESC_INDICATOR_PTR
| ARD
| records
| StrLen_or_IndPtr argument in SQLBindCol
|
SQL_DESC_OCTET_LENGTH
| ARD
| records
| BufferLength argument in SQLBindCol
|
SQL_DESC_OCTET_LENGTH_PTR
| ARD
| records
| StrLen_or_IndPtr argument in SQLBindCol
|
SQL_DESC_ROWS_
PROCESSED_PTR
| IRD
| header
| SQL_ATTR_ROWS_FETCHED_PTR statement attribute
|
SQL_DESC_TYPE
| ARD
| records
| TargetType argument in SQLBindCol
|
All descriptor fields can also be set through SQLSetDescField.
Separate Length and Indicator Buffers
Applications can bind a single buffer or two separate buffers to be used to
hold length and indicator values. When an application calls SQLBindCol, the driver sets the SQL_DESC_OCTET_LENGTH_PTR and SQL_DESC_INDICATOR_PTR
fields of the ARD to the same address, which is passed in the StrLen_or_IndPtr argument. When an application calls SQLSetDescField or SQLSetDescRec, it can set these two fields to different addresses.
SQLFetch determines whether the application has specified separate length and
indicator buffers. In this case, when the data is not NULL, SQLFetch sets the indicator buffer to 0 and returns the length in the length buffer.
When the data is NULL, SQLFetch sets the indicator buffer to SQL_NULL_DATA and does not modify the length
buffer.
Code Example
See SQLBindCol, SQLColumns, SQLGetData, and SQLProcedures.
Related Functions
For information about
| See
|