MDAC 2.5 SDK - ODBC Programmer's Reference
Chapter 21: ODBC API Reference

SQLGetDiagField

Conformance

Version Introduced: ODBC 3.0
Standards Compliance: ISO 92

Summary

SQLGetDiagField returns the current value of a field of a record of the diagnostic data structure (associated with a specified handle) that contains error, warning, and status information.

Syntax

SQLRETURN SQLGetDiagField(
     SQLSMALLINT     HandleType,
     SQLHANDLE     Handle,
     SQLSMALLINT     RecNumber,
     SQLSMALLINT     DiagIdentifier,
     SQLPOINTER     DiagInfoPtr,
     SQLSMALLINT     BufferLength,
     SQLSMALLINT *     StringLengthPtr);

Arguments

HandleType

[Input]
A handle type identifier that describes the type of handle for which diagnostics are required. Must be one of the following:

SQL_HANDLE_ENV
SQL_HANDLE_DBC
SQL_HANDLE_STMT
SQL_HANDLE_DESC

Handle

[Input]
A handle for the diagnostic data structure, of the type indicated by HandleType. If HandleType is SQL_HANDLE_ENV, Handle can be either a shared or an unshared environment handle.

RecNumber

[Input]
Indicates the status record from which the application seeks information. Status records are numbered from 1. If the DiagIdentifier argument indicates any field of the diagnostics header, RecNumber is ignored. If not, it should be greater than 0.

DiagIdentifier

[Input]
Indicates the field of the diagnostic whose value is to be returned. For more information, see the "DiagIdentifier Argument" section in "Comments."

DiagInfoPtr

[Output]
Pointer to a buffer in which to return the diagnostic information. The data type depends on the value of DiagIdentifier.

BufferLength

[Input]
If DiagIdentifier is an ODBC-defined diagnostic and DiagInfoPtr points to a character string or a binary buffer, this argument should be the length of *DiagInfoPtr. If DiagIdentifier is an ODBC-defined field and *DiagInfoPtr is an integer, BufferLength is ignored. If the value in *DiagInfoPtr is a Unicode string (when calling SQLGetDiagFieldW), the BufferLength argument must be an even number.

If DiagIdentifier is a driver-defined field, the application indicates the nature of the field to the Driver Manager by setting the BufferLength argument. BufferLength can have the following values:

• If *ValuePtr is a pointer to a character string, then BufferLength is the length of the string or SQL_NTS.
  
  
• If *ValuePtr is a pointer to a binary buffer, then the application places the result of the SQL_LEN_BINARY_ATTR(length) macro in BufferLength. This places a negative value in BufferLength.
  
  
• If *ValuePtr is a pointer to a value other than a character string or binary string, then BufferLength should have the value SQL_IS_POINTER.
  
  
• If *ValuePtr is contains a fixed-length data type, then BufferLength is SQL_IS_INTEGER, SQL_IS_UINTEGER, SQL_IS_SMALLINT, or SQL_IS_USMALLINT, as appropriate.

StringLengthPtr

[Output]
Pointer to a buffer in which to return the total number of bytes (excluding the number of bytes required for the null-termination character) available to return in *DiagInfoPtr, for character data. If the number of bytes available to return is greater than BufferLength, the text in *DiagInfoPtr is truncated to BufferLength minus the length of a null-termination character.

Returns

SQL_SUCCESS, SQL_SUCCESS_WITH_INFO, SQL_ERROR, SQL_INVALID_HANDLE, or SQL_NO_DATA.

Diagnostics

SQLGetDiagField does not post diagnostic records for itself. It uses the following return values to report the outcome of its own execution:

• SQL_SUCCESS: The function successfully returned diagnostic information.
  
  
• SQL_SUCCESS_WITH_INFO: *DiagInfoPtr was too small to hold the requested diagnostic field, so the data in the diagnostic field was truncated. To determine that a truncation occurred, the application must compare BufferLength to the actual number of bytes available, which is written to *StringLengthPtr.
  
  
• SQL_INVALID_HANDLE: The handle indicated by HandleType and Handle was not a valid handle.
  
  
• SQL_ERROR: One of the following occurred:
  • The DiagIdentifier argument was not one of the valid values.
    
    
  • The DiagIdentifier argument was SQL_DIAG_CURSOR_ROW_COUNT, SQL_DIAG_DYNAMIC_FUNCTION, SQL_DIAG_DYNAMIC_FUNCTION_CODE, or SQL_DIAG_ROW_COUNT, but Handle was not a statement handle. (The Driver Manager returns this diagnostic.)
    
    
  • The RecNumber argument was negative or 0 when DiagIdentifier indicated a field from a diagnostic record. RecNumber is ignored for header fields.
    
    
  • The value requested was a character string and BufferLength was less than zero.
• SQL_NO_DATA: RecNumber was greater than the number of diagnostic records that existed for the handle specified in Handle. The function also returns SQL_NO_DATA for any positive RecNumber if there are no diagnostic records for Handle.

Comments

An application typically calls SQLGetDiagField to accomplish one of three goals:

1. To obtain specific error or warning information when a function call has returned SQL_ERROR or SQL_SUCCESS_WITH_INFO (or SQL_NEED_DATA for the SQLBrowseConnect function).
   
   
2. To find out the number of rows in the data source that were affected when insert, delete, or update operations were performed with a call to SQLExecute, SQLExecDirect, SQLBulkOperations, or SQLSetPos (from the SQL_DIAG_ROW_COUNT header field), or to find out the number of rows that exist in the current open cursor, if the driver is able to provide this information (from the SQL_DIAG_CURSOR_ROW_COUNT header field).
   
   
3. To determine which function was executed by a call to SQLExecDirect or SQLExecute (from the SQL_DIAG_DYNAMIC_FUNCTION and SQL_DIAG_DYNAMIC_FUNCTION_CODE header fields).

Any ODBC function can post zero or more diagnostic records each time it is called, so an application can call SQLGetDiagField after any ODBC function call. There is no limit to the number of diagnostic records that can be stored at any one time. SQLGetDiagField retrieves only the diagnostic information most recently associated with the diagnostic data structure specified in the Handle argument. If the application calls an ODBC function other than SQLGetDiagField or SQLGetDiagRec, any diagnostic information from a previous call with the same handle is lost.

An application can scan all diagnostic records by incrementing RecNumber, as long as SQLGetDiagField returns SQL_SUCCESS. The number of status records is indicated in the SQL_DIAG_NUMBER header field. Calls to SQLGetDiagField are nondestructive to the header and record fields. The application can call SQLGetDiagField again at a later time to retrieve a field from a record, as long as a function other than the diagnostic functions has not been called in the interim, which would post records on the same handle.

An application can call SQLGetDiagField to return any diagnostic field at any time, with the exception of SQL_DIAG_CURSOR_ROW_COUNT or SQL_DIAG_ROW_COUNT, which will return SQL_ERROR if Handle is not a statement handle. If any other diagnostic field is undefined, the call to SQLGetDiagField will return SQL_SUCCESS (provided no other diagnostic is encountered) and an undefined value is returned for the field.

For more information, see "Using SQLGetDiagRec and SQLGetDiagField" and "Implementing SQLGetDiagRec and SQLGetDiagField" in Chapter 15, "Diagnostics."

HandleType Argument

Each handle type can have diagnostic information associated with it. The HandleType argument denotes the handle type of Handle.

Some header and record fields cannot be returned for environment, connection, statement, and descriptor handles. Those handles for which a field is not applicable are indicated in the "Header Fields" and "Record Fields" sections following.

If HandleType is SQL_HANDLE_ENV, Handle can be either a shared or unshared environment handle.

No driver-specific header diagnostic fields should be associated with an environment handle.

The only diagnostic header fields that are defined for a descriptor handle are SQL_DIAG_NUMBER and SQL_DIAG_RETURNCODE.

DiagIdentifier Argument

This argument indicates the identifier of the field required from the diagnostic data structure. If RecNumber is greater than or equal to 1, the data in the field describes the diagnostic information returned by a function. If RecNumber is 0, the field is in the header of the diagnostic data structure and therefore contains data pertaining to the function call that returned the diagnostic information, not to the specific information.

Drivers can define driver-specific header and record fields in the diagnostic data structure.

An ODBC 3.x application working with an ODBC 2.x driver will be able to call SQLGetDiagField only with a DiagIdentifier argument of SQL_DIAG_CLASS_ORIGIN, SQL_DIAG_CLASS_SUBCLASS_ORIGIN, SQL_DIAG_CONNECTION_NAME, SQL_DIAG_MESSAGE_TEXT, SQL_DIAG_NATIVE, SQL_DIAG_NUMBER, SQL_DIAG_RETURNCODE, SQL_DIAG_SERVER_NAME, or SQL_DIAG_SQLSTATE. All other diagnostic fields will return SQL_ERROR.

Header Fields

The header fields listed in the following table can be included in the DiagIdentifier argument.

Record Fields

The record fields listed in the following table can be included in the DiagIdentifier argument.

Values of the Dynamic Function Fields

The following table describes the values of SQL_DIAG_DYNAMIC_FUNCTION and SQL_DIAG_DYNAMIC_FUNCTION_CODE that apply to each type of SQL statement executed by a call to SQLExecute or SQLExecDirect. The driver can add driver-defined values to those listed.

Sequence of Status Records

Status records are placed in a sequence based on row number and the type of the diagnostic. The Driver Manager determines the final order in which to return status records that it generates. The driver determines the final order in which to return status records that it generates.

If diagnostic records are posted by both the Driver Manager and the driver, the Driver Manager is responsible for ordering them.

If there are two or more status records, the sequence of the records is determined first by row number. The following rules apply to determining the sequence of diagnostic records by row:

• Records that do not correspond to any row appear in front of records that correspond to a particular row, because SQL_NO_ROW_NUMBER is defined to be –1.
  
  
• Records for which the row number is unknown appear in front of all other records, because SQL_ROW_NUMBER_UNKNOWN is defined to be –2.
  
  
• For all records that pertain to specific rows, records are sorted by the value in the SQL_DIAG_ROW_NUMBER field. All errors and warnings of the first row affected are listed, then all errors and warnings of the next row affected, and so on.

Note   The ODBC 3.x Driver Manager does not order status records in the diagnostic queue if SQLSTATE 01S01 (Error in row) is returned by an ODBC 2.x driver or if SQLSTATE 01S01 (Error in row) is returned by an ODBC 3.x driver when SQLExtendedFetch is called or SQLSetPos is called on a cursor that has been positioned with SQLExtendedFetch.

Within each row, or for all those records that do not correspond to a row or for which the row number is unknown, or for all those records with a row number equal to SQL_NO_ROW_NUMBER, the first record listed is determined using a set of sorting rules. After the first record, the order of the other records affecting a row is undefined. An application cannot assume that errors precede warnings after the first record. Applications should scan the entire diagnostic data structure to obtain complete information on an unsuccessful call to a function.

The following rules are used to determine the first record within a row. The record with the highest rank is the first record. The source of a record (Driver Manager, driver, gateway, and so on) is not considered when ranking records.

• Errors. Status records that describe errors have the highest rank. The following rules are applied to sort errors:
  • Records that indicate a transaction failure or possible transaction failure outrank all other records.
    
    
  • If two or more records describe the same error condition, then SQLSTATEs defined by the X/Open CLI specification (classes 03 through HZ) outrank ODBC- and driver-defined SQLSTATEs.
• Implementation-defined No Data values. Status records that describe driver-defined No Data values (class 02) have the second highest rank.
  
  
• Warnings. Status records that describe warnings (class 01) have the lowest rank. If two or more records describe the same warning condition, then warning SQLSTATEs defined by the X/Open CLI specification outrank ODBC-defined and driver-defined SQLSTATEs.

Related Functions