تحرير

مشاركة عبر

Descriptor Fields

  • مقالة

Descriptors contain header and record fields that completely describe columns or parameters.

A descriptor contains a single copy of the following header fields. Changing a header field affects all columns or parameters.

SQL_DESC_ALLOC_TYPE
SQL_DESC_ARRAY_SIZE
SQL_DESC_ARRAY_STATUS_PTR
SQL_DESC_BIND_OFFSET_PTR

SQL_DESC_BIND_TYPE
SQL_DESC_COUNT
SQL_DESC_ROWS_PROCESSED_PTR

A descriptor contains zero or more descriptor records. Each record describes a column or parameter, depending on the type of descriptor. When a new column or parameter is bound, a new record is added to the descriptor. When a column or parameter is unbound, a record is removed from the descriptor. Each record contains a single copy of the following fields:

SQL_DESC_AUTO_UNIQUE_VALUE
SQL_DESC_BASE_COLUMN_NAME
SQL_DESC_BASE_TABLE_NAME
SQL_DESC_CASE_SENSITIVE
SQL_DESC_CATALOG_NAME
SQL_DESC_CONCISE_TYPE
SQL_DESC_DATA_PTR
SQL_DESC_DATETIME_INTERVAL_CODE
SQL_DESC_DATETIME_INTERVAL_PRECISION
SQL_DESC_DISPLAY_SIZE
SQL_DESC_FIXED_PREC_SCALE
SQL_DESC_INDICATOR_PTR
SQL_DESC_LABEL
SQL_DESC_LENGTH
SQL_DESC_LITERAL_PREFIX
SQL_DESC_LITERAL_SUFFIX

SQL_DESC_LOCAL_TYPE_NAME
SQL_DESC_NAME
SQL_DESC_NULLABLE
SQL_DESC_OCTET_LENGTH
SQL_DESC_OCTET_LENGTH_PTR
SQL_DESC_PARAMETER_TYPE
SQL_DESC_PRECISION
SQL_DESC_SCALE
SQL_DESC_SCHEMA_NAME
SQL_DESC_SEARCHABLE
SQL_DESC_TABLE_NAME
SQL_DESC_TYPE
SQL_DESC_TYPE_NAME
SQL_DESC_UNNAMED
SQL_DESC_UNSIGNED
SQL_DESC_UPDATABLE

Many statement attributes correspond to the header field of a descriptor. Setting these attributes through a call to SQLSetStmtAttr and setting the corresponding descriptor header field by calling SQLSetDescField have the same effect. The same is true for SQLGetStmtAttr and SQLGetDescField, both of which retrieve the same information. Calling the statement functions instead of the descriptor functions has the advantage that a descriptor handle does not have to be retrieved.

The following header fields can be set by setting statement attributes:

SQL_DESC_ARRAY_SIZE
SQL_DESC_ARRAY_STATUS_PTR
SQL_DESC_BIND_OFFSET_PTR

SQL_DESC_BIND_TYPE
SQL_DESC_ROWS_PROCESSED_PTR

This section contains the following topics.