Programming Interfaces Guide

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Application development using Embedded SQL

Chapter 2: The Embedded SQL Interface

Embedded SQL data types

To transfer information between a program and the database server, every piece of data must have a data type. The Embedded SQL data type constants are prefixed with DT_, and can be found in the sqldef.h header file. You can create a host variable of any one of the supported types. You can also use these types in a 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.

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

DT_STRING
NULL-terminated blank-padded 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. When supplying information to the database server, you must set the length field. When fetching information from the database server, the server sets the length field (not padded).
```
typedef struct VARCHAR {
unsigned short int len;
char array[1];
} VARCHAR;
```
DT_BINARY
Varying length binary data with a two byte length field. When supplying information to the database server, you must set the length field. When fetching information from the database server, the server sets the length field.
```
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 structure 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.

For more information, see the DATE_FORMAT, TIME_FORMAT, TIMESTAMP_FORMAT, and DATE_ORDER database options in Database Options .
DT_VARIABLE
NULL-terminated character string. The character string must be the name of a SQL variable whose value is used by the database server. This data type is used only for supplying data to the database server. It cannot be used when fetching data from the database server.

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 .


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