User's Guide

Part V. The SQL Anywhere Programming Interfaces

Chapter 34. The Embedded SQL Interface

In order to transfer information between a program and the database engine, every piece of data must have a data type. The Embedded SQL data type constants (prefixed with DT_) can be found in the SQLDEF.H header file (see "SQLDEF.H header file"). You can create a host variable (next section) of any one of the supported types. You can also use these types in an SQLDA structure for passing data to and from the database.

The following data types are supported by the Embedded SQL programming interface:

• DT_SMALLINT 16 bit, signed integer.
• DT_INT 32 bit, signed integer.
• DT_FLOAT 4 byte floating point number.
• DT_DOUBLE 8 byte floating point number.
• DT_DECIMAL Packed decimal number. Decimal digits are packed into an array of characters, two digits per byte. The most significant digits are stored first. The low order nibble (half-byte) of the last byte is the sign (0xC for positive, 0xD for negative). If the precision is even, the first digit stored is a 0.

       typedef struct DECIMAL {
       char array[1];
       } DECIMAL;
  

• DT_STRING NULL-terminated character string.
• DT_DATE NULL-terminated character string that is a valid date.
• DT_TIME NULL-terminated character string that is a valid time.
• DT_TIMESTAMP NULL-terminated character string that is a valid timestamp.
• DT_FIXCHAR Fixed-length blank padded character string.
• DT_VARCHAR Varying length character string with a two byte length field. The length field must be set when supplying information to the database engine. The database engine will set the length field when you fetch information.

       typedef struct VARCHAR {
       unsigned short int len;
       char array[1];
       } VARCHAR;
  

• DT_BINARY Varying length binary data with a two byte length field. The length field must be set when supplying information to the database engine. The database engine will set the length field when you fetch information.

       typedef struct BINARY {
       unsigned short int len;
       char array[1];
       } BINARY;
  

• DT_TIMESTAMPSTRUCT SQLDATETIME structure with fields for each part of a timestamp.

       typedef struct sqldatetime {
       unsigned short year; /* e.g. 1992 */
       unsigned char month; /* 0-11 */
       unsigned char day_of_week; /* 0-6 0=Sunday */
       unsigned short day_of_year; /* 0-365 */
       unsigned char day; /* 1-31 */
       unsigned char hour; /* 0-23 */
       unsigned char minute; /* 0-59 */
       unsigned char second; /* 0-59 */
       unsigned long microsecond; /* 0-999999 */
       } SQLDATETIME;
  

  The SQLDATETIME struct can be used to retrieve fields of DATE, TIME, and TIMESTAMP type (or anything that can be converted to one of these). Often, applications have their own formats and date manipulation code. Fetching data in this structure makes it easier for a programmer to manipulate this data. Note that DATE, TIME and TIMESTAMP fields can also be fetched and updated with any character type. See the DATE_FORMAT, TIME_FORMAT, TIMESTAMP_FORMAT, and DATE_ORDER database options in "SET OPTION statement".

• DT_VARIABLE NULL-terminated character string. The character string must be the name of a SQL variable whose value will be used by the database engine (see "SET statement"). This data type is only used when supplying data to the database engine. It cannot be used when fetching data from the database engine.

The structures are defined in the SQLCA.H file. The VARCHAR, BINARY and DECIMAL types contain a one-character array and are thus not useful for declaring host variables but they are useful for allocating variables dynamically or typecasting other variables.

DATE and TIME database types

There are no corresponding Embedded SQL interface data types for the various DATE and TIME database types. These database types are all fetched and updated using either the SQLDATETIME structure or character strings.

There are no Embedded SQL interface data types for LONG VARCHAR and LONG BINARY database types. These database types are fetched and updated in pieces. For more information see "GET DATA statement" and "SET statement".