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ASA Programming Interfaces Guide |
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| Chapter 2: The Embedded SQL Interface |
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| The SQL descriptor area (SQLDA) |
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| Length field values |
The sqllen field length of the sqlvar structure in a SQLDA is used in three different kinds of interactions with the database server. The following tables detail each of these interactions. These tables list the interface constant types (the DT_ types) found in the sqldef.h header file. These constants would be placed in the SQLDA sqltype field. The types are described in Embedded SQL data types .
In static SQL, a SQLDA is still used but it is generated and completely filled in by the SQL preprocessor. In this static case, the tables give the correspondence between the static C language host variable types and the interface constants.
The following table indicates the values of the sqllen and sqltype structure members returned by the DESCRIBE command for the various database types (both SELECT LIST and BIND VARIABLE DESCRIBE statements). In the case of a user-defined database data type, the base type is described.
Your program can use the types and lengths returned from a DESCRIBE, or you may use another type. The database server will perform type conversions between any two types. The memory pointed to by the sqldata field must correspond to the sqltype and sqllen fields.
For information on Embedded SQL data types, see Embedded SQL data types .
Database field type | Embedded SQL type returned | Length returned on describe |
BIGINT | DT_BIGINT | 8 |
BINARY(n) | DT_BINARY | n |
BIT | DT_BIT | 1 |
CHAR(n) | DT_FIXCHAR | n |
DATE | DT_DATE | length of longest formatted string |
DECIMAL(p,s) | DT_DECIMAL | high byte of length field in SQLDA set to p, and low byte set to s |
DOUBLE | DT_DOUBLE | 8 |
FLOAT | DT_FLOAT | 4 |
INT | DT_INT | 4 |
LONG BINARY | DT_LONGBINARY | 32767 |
LONG VARCHAR | DT_LONGVARCHAR | 32767 |
REAL | DT_FLOAT | 4 |
SMALLINT | DT_SMALLINT | 2 |
TIME | DT_TIME | length of longest formatted string |
TIMESTAMP | DT_TIMESTAMP | length of longest formatted string |
TINYINT | DT_TINYINT | 1 |
UNSIGNED BIGINT | DT_UNSBIGINT | 8 |
UNSIGNED INT | DT_UNSINT | 4 |
UNSIGNED SMALLINT | DT_UNSSMALLINT | 2 |
VARCHAR(n) | DT_VARCHAR | n |
The following table indicates how you specify lengths of values when you supply data to the database server in the SQLDA.
Only the data types shown in the table are allowed in this case. The DT_DATE, DT_TIME and DT_TIMESTAMP types are treated the same as DT_STRING when supplying information to the database; the value must be a NULL-terminated character string in an appropriate date format.
Embedded SQL Data Type | Program action to set the length |
DT_BIGINT | No action required |
DT_BINARY(n) | length taken from field in BINARY structure |
DT_BIT | No action required |
DT_DATE | length determined by terminating \0 |
DT_DECIMAL(p,s) | high byte of length field in SQLDA set to p, and low byte set to s |
DT_DOUBLE | No action required |
DT_FIXCHAR(n) | length field in SQLDA determines length of string |
DT_FLOAT | No action required |
DT_INT | No action required |
DT_SMALLINT | No action required |
DT_STRING | length determined by terminating \0 |
DT_TIME | length determined by terminating \0 |
DT_TIMESTAMP | length determined by terminating \0 |
DT_TIMESTAMP_STRUCT | No action required |
DT_UNSBIGINT | No action required |
DT_UNSINT | No action required |
DT_UNSSMALLINT | No action required |
DT_VARCHAR(n) | length taken from field in VARCHAR structure |
DT_VARIABLE | length determined by terminating \0 |
The following table indicates the values of the length field when you retrieve data from the database using a SQLDA. The sqllen field is never modified when you retrieve data.
Only the interface data types shown in the table are allowed in this case. The DT_DATE, DT_TIME and DT_TIMESTAMP data types are treated the same as DT_STRING when you retrieve information from the database. The value is formatted as a character string in the current date format.
Embedded SQL Data Type | What the program must set length field to when receiving | How the database returns length information after fetching a value |
DT_BIGINT | No action required | No action required |
DT_BINARY(n) | maximum length of BINARY structure (n+2) | lenfield of BINARY structure set to actual length |
DT_BIT | No action required | No action required |
DT_DATE | length of buffer | \0 at end of string |
DT_DECIMAL(p,s) | high byte set to p and low byte set to s | No action required |
DT_DOUBLE | No action required | No action required |
DT_FIXCHAR(n) | length of buffer | padded with blanks to length of buffer |
DT_FLOAT | No action required | No action required |
DT_INT | No action required | No action required |
DT_SMALLINT | No action required | No action required |
DT_STRING | length of buffer | \0 at end of string |
DT_TIME | length of buffer | \0 at end of string |
DT_TIMESTAMP | length of buffer | \0 at end of string |
DT_TIMESTAMP_ STRUCT | No action required | No action required |
DT_UNSBIGINT | No action required | No action required |
DT_UNSINT | No action required | No action required |
DT_UNSSMALLINT | No action required | No action required |
DT_VARCHAR(n) | maximum length of VARCHAR structure (n+2) | lenfield of VARCHAR structure set to actual length |
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