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SQLExecDirect函數源代碼
static SQLRETURN
ODBCExecDirect(ODBCStmt *stmt, SQLCHAR *szSqlStr, SQLINTEGER nSqlStr)
{
    char *query;
    MapiMsg ret;
    MapiHdl hdl;

    hdl = stmt->hdl;

    if (stmt->State >= EXECUTED1 || (stmt->State == EXECUTED0 && mapi_more_results(hdl))) {
        /* Invalid cursor state */
        addStmtError(stmt, "24000", NULL, 0);
        return SQL_ERROR;
    }

    /* TODO: convert ODBC escape sequences ( {d 'value'} or {t 'value'} or
       {ts 'value'} or {escape 'e-char'} or {oj outer-join} or
       {fn scalar-function} etc. ) to MonetDB SQL syntax */
    query = ODBCTranslateSQL(szSqlStr, (size_t) nSqlStr, stmt->noScan);

    ODBCResetStmt(stmt);

#ifdef ODBCDEBUG
    ODBCLOG("SQLExecDirect: \"%s\"\n", query);
#endif

    ret = mapi_query_handle(hdl, query);
    free(query);
    switch (ret) {
    case MOK:
        break;
    case MTIMEOUT:
        /* Communication link failure */
        addStmtError(stmt, "08S01", mapi_error_str(stmt->Dbc->mid), 0);
        return SQL_ERROR;
    default:
        /* General error */
        addStmtError(stmt, "HY000", mapi_error_str(stmt->Dbc->mid), 0);
        return SQL_ERROR;
    }

    /* now get the result data and store it to our internal data structure */

    return ODBCInitResult(stmt);
}

http://msdn.microsoft.com/en-us/library/ms716303(VS.85).aspx
Freeing a Statement Handle ODBC

As mentioned earlier, it is more efficient to reuse statements than to drop them and allocate new ones. Before executing a new SQL statement on a statement, applications should be sure that the current statement settings are appropriate. These include statement attributes, parameter bindings, and result set bindings. Generally, parameters and result sets for the old SQL statement need to be unbound (by calling SQLFreeStmt with the SQL_RESET_PARAMS and SQL_UNBIND options) and rebound for the new SQL statement.

When the application has finished using the statement, it calls SQLFreeHandle to free the statement. After freeing the statement, it is an application programming error to use the statement's handle in a call to an ODBC function; doing so has undefined but probably fatal consequences.

When SQLFreeHandle is called, the driver releases the structure used to store information about the statement.

SQLDisconnect automatically frees all statements on a connection.

/**********************************************
* ODBCStmt.c
*
* Description:
* This file contains the functions which operate on
* ODBC statement structures/objects (see ODBCStmt.h).
*
* Author: Martin van Dinther
* Date  : 30 aug 2002
*
**********************************************/

#include "ODBCGlobal.h"
#include "ODBCStmt.h"

#define ODBC_STMT_MAGIC_NR  5461    /* for internal sanity check only */

/*
* Creates a new allocated ODBCStmt object and initializes it.
*
* Precondition: none
* Postcondition: returns a new ODBCStmt object
*/
ODBCStmt *
newODBCStmt(ODBCDbc *dbc)
{
    ODBCStmt *stmt = (ODBCStmt *) malloc(sizeof(ODBCStmt));
    assert(stmt);

    assert(dbc);
    assert(dbc->mid);

    if (stmt == NULL) {
        /* Memory allocation error */
        addDbcError(dbc, "HY001", NULL, 0);
        return NULL;
    }

    stmt->Dbc = dbc;
    stmt->Error = NULL;
    stmt->RetrievedErrors = 0;

    stmt->State = INITED;
    stmt->hdl = mapi_new_handle(dbc->mid);
    if (stmt->hdl == NULL) {
        /* Memory allocation error */
        addDbcError(dbc, "HY001", NULL, 0);
        free(stmt);
        return NULL;
    }
    assert(stmt->hdl);

    stmt->currentRow = 0;
    stmt->startRow = 0;
    stmt->rowSetSize = 0;
    stmt->queryid = -1;
    stmt->nparams = 0;
    stmt->querytype = -1;
    stmt->rowcount = 0;

    /* add this stmt to the administrative linked stmt list */
    stmt->next = dbc->FirstStmt;
    dbc->FirstStmt = stmt;

    stmt->cursorType = SQL_CURSOR_FORWARD_ONLY;
    stmt->cursorScrollable = SQL_NONSCROLLABLE;
    stmt->retrieveData = SQL_RD_ON;
    stmt->noScan = SQL_NOSCAN_OFF;

    stmt->ApplRowDescr = newODBCDesc(dbc);
    stmt->ApplParamDescr = newODBCDesc(dbc);
    stmt->ImplRowDescr = newODBCDesc(dbc);
    stmt->ImplParamDescr = newODBCDesc(dbc);
    stmt->AutoApplRowDescr = stmt->ApplRowDescr;
    stmt->AutoApplParamDescr = stmt->ApplParamDescr;

    if (stmt->ApplRowDescr == NULL || stmt->ApplParamDescr == NULL || stmt->ImplRowDescr == NULL || stmt->ImplParamDescr == NULL) {
        destroyODBCStmt(stmt);
        return NULL;
    }

    stmt->ApplRowDescr->sql_desc_alloc_type = SQL_DESC_ALLOC_AUTO;
    stmt->ApplParamDescr->sql_desc_alloc_type = SQL_DESC_ALLOC_AUTO;
    stmt->ImplRowDescr->sql_desc_alloc_type = SQL_DESC_ALLOC_AUTO;
    stmt->ImplParamDescr->sql_desc_alloc_type = SQL_DESC_ALLOC_AUTO;
    stmt->ImplRowDescr->Stmt = stmt;
    stmt->ImplParamDescr->Stmt = stmt;

    stmt->Type = ODBC_STMT_MAGIC_NR;    /* set it valid */

    return stmt;
}

SQLFreeHandle
ODBCFreeStmt_(ODBCStmt *stmt)
{
    /* check if statement is not active */
    if (stmt->State >= EXECUTED0) {
        /* should be closed first */
        if (SQLFreeStmt_(stmt, SQL_CLOSE) == SQL_ERROR)
            return SQL_ERROR;
    }

    /* Ready to destroy the stmt handle */
    destroyODBCStmt(stmt);
    return SQL_SUCCESS;
}

SQLFreeStmt

SQLFreeStmt_(ODBCStmt *stmt, SQLUSMALLINT option)
{
    switch (option) {
    case SQL_CLOSE:
        /* Note: this option is also called from SQLCancel() and
           SQLCloseCursor(), so be careful when changing the code */
        /* close cursor, discard result set, set to prepared */
        setODBCDescRecCount(stmt->ImplRowDescr, 0);
        stmt->currentRow = 0;
        stmt->startRow = 0;
        stmt->rowSetSize = 0;

        if (stmt->State == EXECUTED0)
            stmt->State = stmt->queryid >= 0 ? PREPARED0 : INITED;
        else if (stmt->State >= EXECUTED1)
            stmt->State = stmt->queryid >= 0 ? PREPARED1 : INITED;

        /* Important: do not destroy the bind parameters and columns! */
        return SQL_SUCCESS;
    case SQL_DROP:
        return ODBCFreeStmt_(stmt);
    case SQL_UNBIND:
        setODBCDescRecCount(stmt->ApplRowDescr, 0);
        return SQL_SUCCESS;
    case SQL_RESET_PARAMS:
        setODBCDescRecCount(stmt->ApplParamDescr, 0);
        setODBCDescRecCount(stmt->ImplParamDescr, 0);
        mapi_clear_params(stmt->hdl);
        return SQL_SUCCESS;
    default:
        /* Invalid attribute/option identifier */
        addStmtError(stmt, "HY092", NULL, 0);
        return SQL_ERROR;
    }

    /* not reached */
}

SQLHSTMT的結構
typedef struct tODBCDRIVERSTMT {
    /* Stmt properties */
    int Type;        /* structure type, used for handle validy test */
    ODBCError *Error;    /* pointer to an Error object or NULL */
    int RetrievedErrors;    /* # of errors already retrieved by SQLError */
    ODBCDbc *Dbc;        /* Connection context */
    struct tODBCDRIVERSTMT *next;    /* the linked list of stmt's in this Dbc */
    enum StatementState State;    /* needed to detect invalid cursor state */
    MapiHdl hdl;

    unsigned int rowcount;    /* # affected rows */

    /* startRow is the row number of first row in the result
       set (0 based); rowSetSize is the number of rows in the
       current result set; currentRow is the row number of the
       current row within the current result set */
    unsigned int currentRow;
    unsigned int startRow;
    unsigned int rowSetSize;

    unsigned int currentCol; /* used by SQLGetData() */
    SQLINTEGER retrieved;    /* amount of data retrieved */
    int queryid;        /* the query to be executed */
    int nparams;        /* the number of parameters expected */

    int querytype;        /* query type as returned by server */

    SQLUINTEGER cursorType;
    SQLUINTEGER cursorScrollable;
    SQLUINTEGER retrieveData;
    SQLUINTEGER noScan;

    ODBCDesc *ApplRowDescr;    /* Application Row Descriptor (ARD) */
    ODBCDesc *ApplParamDescr; /* Application Parameter Descriptor (APD) */
    ODBCDesc *ImplRowDescr;    /* Implementation Row Descriptor (IRD) */
    ODBCDesc *ImplParamDescr; /* Implementation Parameter Descriptor (IPD) */

    ODBCDesc *AutoApplRowDescr; /* Auto-allocated ARD */
    ODBCDesc *AutoApplParamDescr; /* Auto-allocated APD */

    /* Stmt children: none yet */
} ODBCStmt;

posted on 2008-09-11 11:31 r2100 閱讀(1151) 評論(2) 編輯收藏引用

Feedback

# re: http://msdn.microsoft.com/en-us/library/ms716303(VS.85).aspx 2008-09-11 11:32 r2100

但是一直沒有找到實例，郁悶回復更多評論

# re: http://msdn.microsoft.com/en-us/library/ms716303(VS.85).aspx 2009-01-28 18:01 張三

安裝不成。。。回復更多評論

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