在具有疏鬆資料行的資料表上呼叫 SQLColumns

發行項
05/07/2013

此範例會示範如何在已使用 SQL Server Native Client 中之 ODBC 定義疏鬆資料行的資料表上呼叫 SQLColumns。

此範例不適用於 SQL Server 2008 之前的任何 SQL Server 版本。

如需有關疏鬆資料行功能的詳細資訊，請參閱＜SQL Server Native Client 中的疏鬆資料行支援＞。

範例

第一個清單是 C++ 原始程式碼。請將 "MyServer" 變更為有效的伺服器名稱。請確認您的 INCLUDE 環境變數包含的目錄內含 sqlncli.h。如果您要建立並執行此範例，當做 64 位元作業系統上的 32 位元應用程式，您必須利用 %windir%\SysWOW64\odbcad32.exe，以 ODBC 管理員身分建立 ODBC 資料來源。

這個範例會連接到電腦的預設 SQL Server 執行個體。若要連接到具名執行個體，請變更 ODBC 資料來源的定義，以便使用下列格式指定執行個體：server\namedinstance。根據預設，SQL Server Express 會安裝至具名執行個體。

使用 /EHsc /D、"UNICODE" 和 odbc32.lib 編譯。

第二個 (Transact-SQL) 程式碼清單會刪除此範例所建立的資料表。

// compile with: /EHsc /D "UNICODE" odbc32.lib
#include <windows.h>
#include <stdio.h>
#include <sqlext.h>

#include <sqlncli.h>

#define SUCCESS(x) (!((x) & 0xFFFE))

#define CHKRC(stmt) rc = (stmt); \
   if (!SUCCESS(rc)) \
   throw (RETCODE) rc;

void PrintError(SQLSMALLINT HandleType, SQLHANDLE Handle) {
   RETCODE rc = SQL_SUCCESS;
   SQLTCHAR szSqlState[6], szMessage[1024];
   SQLSMALLINT i = 1, msgLen = 0;
   SQLINTEGER NativeError;

   do {
      i = 1;
      while (SQL_NO_DATA != (rc = SQLGetDiagRec(HandleType, Handle, i, szSqlState, &NativeError, 
         szMessage, sizeof(szMessage)/sizeof(SQLTCHAR), &msgLen)) && SUCCESS(rc)) {
            wprintf(L"SQLState=%s, NativeError=%ld, Message=%s\r\n", szSqlState, NativeError, szMessage);
            i++;
      }
   } 
   while (SQL_NO_DATA != (rc = SQLMoreResults(Handle)) && SUCCESS(rc));
}

#define STR_LEN 128 + 1
#define REM_LEN 254 + 1

void ProcessSQLColumnsResult(SQLHSTMT hstmt) {
   SQLCHAR szSchema[STR_LEN];
   SQLCHAR szCatalog[STR_LEN];
   SQLCHAR szColumnName[STR_LEN];
   SQLCHAR szTableName[STR_LEN];
   SQLCHAR szTypeName[STR_LEN];
   SQLCHAR szRemarks[REM_LEN];
   SQLCHAR szColumnDefault[STR_LEN];
   SQLCHAR szIsNullable[STR_LEN];

   SQLINTEGER ColumnSize;
   SQLINTEGER BufferLength;
   SQLINTEGER CharOctetLength;
   SQLINTEGER OrdinalPosition;

   SQLSMALLINT DataType;
   SQLSMALLINT DecimalDigits;
   SQLSMALLINT NumPrecRadix;
   SQLSMALLINT Nullable;
   SQLSMALLINT SQLDataType;
   SQLSMALLINT DatetimeSubtypeCode;
   SQLLEN cbCatalog;
   SQLLEN cbSchema;
   SQLLEN cbTableName;
   SQLLEN cbColumnName;
   SQLLEN cbDataType;
   SQLLEN cbTypeName;
   SQLLEN cbColumnSize;
   SQLLEN cbBufferLength;
   SQLLEN cbDecimalDigits;
   SQLLEN cbNumPrecRadix;
   SQLLEN cbNullable;
   SQLLEN cbRemarks;
   SQLLEN cbColumnDefault;
   SQLLEN cbSQLDataType;
   SQLLEN cbDatetimeSubtypeCode;
   SQLLEN cbCharOctetLength;
   SQLLEN cbOrdinalPosition;
   SQLLEN cbIsNullable;

   SQLRETURN rc = SQL_SUCCESS;

   CHKRC(SQLColumns(hstmt, L"tempdb", SQL_NTS, L"dbo", SQL_NTS, L"tbl_sparse_test", SQL_NTS, NULL, 0 ));

   // Bind columns in result set to buffers
   SQLBindCol(hstmt, 1,  SQL_C_CHAR,   szCatalog,              STR_LEN,    &cbCatalog);
   SQLBindCol(hstmt, 2,  SQL_C_CHAR,   szSchema,               STR_LEN,    &cbSchema);
   SQLBindCol(hstmt, 3,  SQL_C_CHAR,   szTableName,            STR_LEN,    &cbTableName);
   SQLBindCol(hstmt, 4,  SQL_C_CHAR,   szColumnName,           STR_LEN,    &cbColumnName);
   SQLBindCol(hstmt, 5,  SQL_C_SSHORT, &DataType,              0,          &cbDataType);
   SQLBindCol(hstmt, 6,  SQL_C_CHAR,   szTypeName,             STR_LEN,    &cbTypeName);
   SQLBindCol(hstmt, 7,  SQL_C_SLONG,  &ColumnSize,            0,          &cbColumnSize);
   SQLBindCol(hstmt, 8,  SQL_C_SLONG,  &BufferLength,          0,          &cbBufferLength);
   SQLBindCol(hstmt, 9,  SQL_C_SSHORT, &DecimalDigits,         0,          &cbDecimalDigits);
   SQLBindCol(hstmt, 10, SQL_C_SSHORT, &NumPrecRadix,          0,          &cbNumPrecRadix);
   SQLBindCol(hstmt, 11, SQL_C_SSHORT, &Nullable,              0,          &cbNullable);
   SQLBindCol(hstmt, 12, SQL_C_CHAR,   szRemarks,              REM_LEN,    &cbRemarks);
   SQLBindCol(hstmt, 13, SQL_C_CHAR,   szColumnDefault,        STR_LEN,    &cbColumnDefault);
   SQLBindCol(hstmt, 14, SQL_C_SSHORT, &SQLDataType,           0,          &cbSQLDataType);
   SQLBindCol(hstmt, 15, SQL_C_SSHORT, &DatetimeSubtypeCode,   0,          &cbDatetimeSubtypeCode);
   SQLBindCol(hstmt, 16, SQL_C_SLONG,  &CharOctetLength,       0,          &cbCharOctetLength);
   SQLBindCol(hstmt, 17, SQL_C_SLONG,  &OrdinalPosition,       0,          &cbOrdinalPosition);
   SQLBindCol(hstmt, 18, SQL_C_CHAR,   szIsNullable,           STR_LEN,    &cbIsNullable);

   try {
      while (SQL_SUCCESS == rc) {
         CHKRC(SQLFetch(hstmt));
         wprintf(L"Column name: %hs\tIsNullable: %hs\tType: %hs\n", szColumnName, szIsNullable, szTypeName);
      }
   }
   catch (RETCODE retcode) {
      if (SQL_NO_DATA != retcode)
         throw retcode;
   }
   SQLFreeStmt(hstmt, SQL_CLOSE);
}

int main() {
   RETCODE rc = SQL_SUCCESS;
   HENV henv = SQL_NULL_HENV;
   HDBC hdbc = SQL_NULL_HDBC;
   SQLHSTMT hstmt = SQL_NULL_HSTMT;
   SQLTCHAR * pszConnection = L"DRIVER={SQL Server Native Client 10.0}; Server=MyServer; Trusted_Connection=Yes;";

   try {
      CHKRC(SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HENV, &henv));
      CHKRC(SQLSetEnvAttr(henv, SQL_ATTR_ODBC_VERSION, (SQLPOINTER)SQL_OV_ODBC3, 0));
      CHKRC(SQLAllocHandle(SQL_HANDLE_DBC, henv, &hdbc));
      CHKRC(SQLDriverConnect( hdbc, NULL, pszConnection, SQL_NTS, NULL, 0, NULL, SQL_DRIVER_NOPROMPT));
      CHKRC(SQLAllocHandle(SQL_HANDLE_STMT, hdbc, &hstmt));
      CHKRC(SQLExecDirect(hstmt,
         L"if object_id('tempdb.dbo.tbl_sparse_test','U') is not null drop table tempdb.dbo.tbl_sparse_test",
         SQL_NTS));

      // Create a new table
      CHKRC(SQLExecDirect(hstmt,
         L"create table tempdb.dbo.tbl_sparse_test (col1 int SPARSE, col2 int, col3 XML column_set for all_sparse_columns)",
         SQL_NTS));

      // Insert a row into the table
      CHKRC(SQLExecDirect(hstmt,
         L"insert tempdb.dbo.tbl_sparse_test (col1, col2) values (1,2)",
         SQL_NTS));

      wprintf(L"Checking default SQLColumns behavior.\nYou should not see the first sparse column.\n");

      ProcessSQLColumnsResult(hstmt);

      wprintf(L"\nChecking SQLColumns with the statement attribute SQL_SS_NAME_SCOPE_EXTENDED.\nYou should see all the columns\n");
      CHKRC(SQLSetStmtAttr(hstmt, SQL_SOPT_SS_NAME_SCOPE, (SQLPOINTER)SQL_SS_NAME_SCOPE_EXTENDED, SQL_IS_SMALLINT));

      ProcessSQLColumnsResult(hstmt);

      wprintf(L"\nChecking SQLColumns with the statement attribute SQL_SS_NAME_SCOPE_SPARSE_COLUMN_SET.\nYou should see only the sparse columns\n");
      CHKRC(SQLSetStmtAttr(hstmt, SQL_SOPT_SS_NAME_SCOPE, (SQLPOINTER)SQL_SS_NAME_SCOPE_SPARSE_COLUMN_SET, SQL_IS_SMALLINT));

      ProcessSQLColumnsResult(hstmt);

   }
   catch (RETCODE retcode) {
      rc = retcode;
   }

   if (!SUCCESS(rc)) {
      if (hstmt)
         PrintError(SQL_HANDLE_STMT, hstmt);
      else if (hdbc)
         PrintError(SQL_HANDLE_DBC, hdbc);
      else if(henv)
         PrintError(SQL_HANDLE_ENV, henv);
   }

   if (hstmt)
      SQLFreeHandle(SQL_HANDLE_STMT, hstmt);
   if (hdbc) {
      SQLDisconnect(hdbc);
      SQLFreeHandle(SQL_HANDLE_DBC, hdbc);
   }
   if (henv)
      SQLFreeHandle(SQL_HANDLE_ENV, henv);
}

use tempdb
IF EXISTS (SELECT name FROM sysobjects WHERE name = 'tbl_sparse_test')
     DROP TABLE tbl_sparse_test
GO

共用方式為

在具有疏鬆資料行的資料表上呼叫 SQLColumns

範例

其他資源