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C Interval Structure

Each of the C interval data types listed in the C Data Types section uses the same structure to contain the interval data. When SQLFetch, SQLFetchScroll, or SQLGetData is called, the driver returns data into the SQL_INTERVAL_STRUCT structure, uses the value that was specified by the application for the C data types (in the call to SQLBindCol, SQLGetData, or SQLBindParameter) to interpret the contents of SQL_INTERVAL_STRUCT, and populates the interval_type field of the structure with the enum value corresponding to the C type. Note that drivers do not read the interval_type field to determine the type of the interval; they retrieve the value of the SQL_DESC_CONCISE_TYPE descriptor field. When the structure is used for parameter data, the driver uses the value specified by the application in the SQL_DESC_CONCISE_TYPE field of the APD to interpret the contents of SQL_INTERVAL_STRUCT, even if the application sets the value of the interval_type field to a different value.

This structure is defined as follows:

typedef struct tagSQL_INTERVAL_STRUCT
{
   SQLINTERVAL interval_type; 
   SQLSMALLINT interval_sign;
   union {
         SQL_YEAR_MONTH_STRUCT   year_month;
         SQL_DAY_SECOND_STRUCT   day_second;
         } intval;
} SQL_INTERVAL_STRUCT;
typedef enum 
{
   SQL_IS_YEAR = 1,
   SQL_IS_MONTH = 2,
   SQL_IS_DAY = 3,
   SQL_IS_HOUR = 4,
   SQL_IS_MINUTE = 5,
   SQL_IS_SECOND = 6,
   SQL_IS_YEAR_TO_MONTH = 7,
   SQL_IS_DAY_TO_HOUR = 8,
   SQL_IS_DAY_TO_MINUTE = 9,
   SQL_IS_DAY_TO_SECOND = 10,
   SQL_IS_HOUR_TO_MINUTE = 11,
   SQL_IS_HOUR_TO_SECOND = 12,
   SQL_IS_MINUTE_TO_SECOND = 13
} SQLINTERVAL;

typedef struct tagSQL_YEAR_MONTH
{
   SQLUINTEGER year;
   SQLUINTEGER month; 
} SQL_YEAR_MONTH_STRUCT;

typedef struct tagSQL_DAY_SECOND
{
   SQLUINTEGER day;
   SQLUINTEGER hour;
   SQLUINTEGER minute;
   SQLUINTEGER second;
   SQLUINTEGER fraction;
} SQL_DAY_SECOND_STRUCT;

The interval_type field of the SQL_INTERVAL_STRUCT indicates to the application what structure is held in the union and also what members of the structure are relevant. The interval_sign field has the value SQL_FALSE if the interval leading field is unsigned; if it is SQL_TRUE, the leading field is negative. The value in the leading field itself is always unsigned, regardless of the value of interval_sign. The interval_sign field acts as a sign bit.

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