ct_dynsqlda

Description

Operate on a SQLDA structure.

Syntax

CS_RETCODE ct_dynsqlda(cmd, sqlda_type, dap, operation)
 
 CS_COMMAND    *cmd;
 CS_INT                 sqlda_type;
 SQLDA                  *dap;
 CS_INT                 operation;

Parameters

Returns

ct_dynsqlda returns the following values:

Usage

• A SQLDA structure is used with prepared dynamic SQL statements. It contains format descriptions and (optionally) values for command input parameters or result columns.

• For more information about dynamic SQL, see Chapter 8, “Using Dynamic SQL Commands,” in the Open Client Client-Library/C Programmer's Guide.

• ct_dynsqlda manages a SQLDA structure. A SQLDA structure contains data areas for the descriptions and values of a command’s input parameters or result values.

• The Sybase-style SQLDA is a self-describing, variable-length structure, declared as follows:

  typedef struct _sqlda
  

   {
  

       CS_SMALLINT sd_sqln; /* Actual length of column array    */
  

       CS_SMALLINT sd_sqld; /* Current number of columns        */
  

       /*
  

       ** The following array is treated as if it were the length 
  

       ** indicated by sd_sqln.
  

       */
  

       struct _sd_column
  

       {
  

           CS_DATAFMT sd_datafmt; /* Format of column i.       */
  

           CS_VOID *sd_sqldata;   /* Value buffer for column i. */
  

           CS_INT sd_sqllen;      /* Length of current value.   */
  

           CS_SMALLINT sd_sqlind; /* Indicator for column i.    */
  

           CS_VOID *sd_sqlmore;   /* Reserved for future use.   */
  

       } sd_column[1];
  

   } sqlda;
  

   #define SYB_SQLDA_SIZE(n) (sizeof(sqlda) \
  

           - sizeof(struct _sd_column) \
  

                   + (n) * sizeof(struct _sd_column))
  

• The application is responsible for correctly allocating and initializing the structure pointed to by dap. The actual size of the structure depends on the number of columns that the structure is to describe. An application can use the SYB_SQLDA_SIZE macro to allocate a SQLDA buffer of the appropriate size. On a system that uses malloc to allocate memory, this can be done as follows:

  #define MAX_COLUMNS 16
  

   SQLDA *dap;
  

   dap = (SQLDA *) malloc( 
  

                    SYB_SQLDA_SIZE(MAX_COLUMNS) );
  

   if (dap == (SQLDA *) NULL)
  

     ... out of memory ...
  

   memset((void *)dap, 0,
  

          SYB_SQLDA_SIZE(MAX_COLUMNS));
  

   dap->sd_sqln = MAX_COLUMNS;
  

  An application can invoke the SQLDA_DECL macro to declare a static SQLDA structure. The invocation:

  SQLDA_DECL(name, size);
  

  Is equivalent to the declaration:

  struct { 
  

           CS_SMALLINT sd_sqln; 
  

           CS_SMALLINT sd_sqld; 
  

           struct { 
  

                   CS_DATAFMT sd_datafmt; 
  

                   CS_VOID *sd_sqldata; 
  

                   CS_SMALLINT sd_sqlind; 
  

                   CS_INT sd_sqllen; 
  

                   CS_VOID *sd_sqlmore; 
  

           } sd_column[(size)]; 
  

   } name;
  

• If the structure will be used to pass input parameters or retrieve results, the (using ct_dynsqlda’s CS_SQLDA_PARAM or CS_SQLDA_BIND operations), then the application must also allocate buffers for item values and set the buffer lengths in the structure.

• The use of the Sybase-style SQLDA is explained in the following sections.

See also