SQLDescribeParam

SQLDescribeParam

SQLDescibe returns the SQL data types of the columns related to the parameter marker (?) of the dynamic SQL statements, size, data types, expressions of the corresponding parameter markers, number of decimal values, and the NULLability

Syntax

SQLRETURN   SQLDescribeParam (
    SQLHSTMT        stmt,
    SQLSMALLINT     iparam,
    SQLSMALLINT *   type,
    SQLINTEGER *    size,
    SQLSMALLINT *   decimaldigit,
    SQLSMALLINT *   nullable );

Arguments

Data Type	Argument	In/Output	Description
SQLHSTMT	stmt	Input	Statement handle
SQLSMALLINT	iparam	Input	Order of the parameter marker, starting with 1
SQLSMALLINT *	type	Output	SQL data type pointer of the parameter
SQLINTEGER *	size	Output	SQL data type pointer of the parameter. Column size or expression pointer of the corresponding parameter
SQLSMALLINT *	decimaldigit	Output	Number of decimal values of the column, expression pointer of the corresponding parameter
SQLSMALLINT *	nullable	Output	Pointer of the value that shows whether NULL is allowed for the parameter or not

Return Values

SQL_SUCCESS
SQL_SUCCESS_WITH_INFO
SQL_INVALID_HANDLE
SQL_ERROR

Description

Parameter iparam is identified by the number. It is numbered from the left to the right starting with 1.

SQLPrepare() must be called before this function.

Before SQLBindParameter(), SQLDescribeParam() must be called.

types, sizes, decimal digits, and NULLable of the parameter have the following limitations:

• type: SQL_VARCHAR

• size: 4000

• decimaldigit: 0

• nullable: SQL_NULLABLE_UNKNOWN - The Altibase CLI driver cannot decide whether the parameter allows NULL data.

Diagnosis

SQLSTATE	Description	Comments
07009	Invalid column number	iparam is out of the entire argument range
HY010	Error in function-calling order	Called before SQLPrepare() / SQLExecDirect()

Related Functions

SQLExecDirect
SQLNumParams
SQLPrepare

Example

< Refer to: $ALTIBASE_HOME/sample/SQLCLI/demo_info2.cpp >

SQLPrepare(hstmt, Statement, SQL_NTS);

// Check to see if there are any parameters. If so, process them.
SQLNumParams(hstmt, &NumParams);
if (NumParams) {
   // Allocate memory for three arrays. The first holds pointers to buffers in which
   // each parameter value will be stored in character form. The second contains the
   // length of each buffer. The third contains the length/indicator value for each
   // parameter.
   PtrArray = (SQLPOINTER *) malloc(NumParams * sizeof(SQLPOINTER));
   BufferLenArray = (SQLINTEGER *) malloc(NumParams * sizeof(SQLINTEGER));
   LenOrIndArray = (SQLINTEGER *) malloc(NumParams * sizeof(SQLINTEGER));

   for (i = 0; i < NumParams; i++) {
   // Describe the parameter.
   SQLDescribeParam(hstmt, i + 1, &DataType, &ParamSize, &DecimalDigits, &Nullable);

   // Call a helper function to allocate a buffer in which to store the parameter
   // value in character form. The function determines the size of the buffer from
   // the SQL data type and parameter size returned by SQLDescribeParam and returns
   // a pointer to the buffer and the length of the buffer.
   PtrArray[i] = (char*)malloc(ParamSize);
   BufferLenArray[i] = SQL_NTS;


   // Bind the memory to the parameter. Assume that we only have input parameters.
   SQLBindParameter(hstmt, i + 1, SQL_PARAM_INPUT, SQL_C_CHAR, DataType, ParamSize,
         DecimalDigits, PtrArray[i], BufferLenArray[i],
         &LenOrIndArray[i]);

   // Prompt the user for the value of the parameter and store it in the memory
   // allocated earlier. For simplicity, this function does not check the value
   // against the information returned by SQLDescribeParam. Instead, the driver does
   // this when the statement is executed.
   strcpy((char*)PtrArray[i], "AAAAAAA");
   BufferLenArray[i] = 7;
   }
}