COLUMNS Rowset | Microsoft OLE DB 2.0 Programmers Reference and Data Access SDK (Microsoft Professional Editions)

OLE DB Programmer's Reference

GUID: DBSCHEMA_COLUMNS

Number of restriction columns: 4

Restriction columns: TABLE_CATALOG, TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME

Default sort order: TABLE_CATALOG, TABLE_SCHEMA, TABLE_NAME

Description: The COLUMNS rowset identifies the columns of tables (including views) defined in the catalog that are accessible to a given user.

Column name	Type indicator	Description
TABLE_CATALOG	DBTYPE_WSTR	Catalog name. NULL if the provider does not support catalogs.
TABLE_SCHEMA	DBTYPE_WSTR	Unqualified schema name. NULL if the provider does not support schemas.
TABLE_NAME	DBTYPE_WSTR	Table name. This column cannot contain a NULL.
COLUMN_NAME	DBTYPE_WSTR	The name of the column; this might not be unique. If this cannot be determined, a NULL is returned. This column, together with the COLUMN_GUID and COLUMN_PROPID columns, forms the column ID. One or more of these columns will be NULL, depending on which elements of the DBID structure the provider uses. If possible, the resulting column ID should be persistent. However, some providers do not support persistent identifiers for columns. The column ID of a base table should be invariant under views.
COLUMN_GUID	DBTYPE_GUID	Column GUID. Providers that do not use GUIDs to identify columns should return NULL in this column.
COLUMN_PROPID	DBTYPE_UI4	Column property ID. Providers that do not associate PROPIDs with columns should return NULL in this column.
ORDINAL_POSITION	DBTYPE_UI4	The ordinal of the column. Columns are numbered starting from one. NULL if there is no stable ordinal value for the column.
COLUMN_HASDEFAULT	DBTYPE_BOOL	VARIANT_TRUE—The column has a default value. VARIANT_FALSE—The column does not have a default value, or it is unknown whether the column has a default value.
COLUMN_DEFAULT	DBTYPE_WSTR	Default value of the column. A provider may expose DBCOLUMN_DEFAULTVALUE but not DBCOLUMN_HASDEFAULT (for SQL-92 tables) in the rowset returned by IColumnsRowset::GetColumnsRowset. If the default value is the NULL value, COLUMN_HASDEFAULT is VARIANT_TRUE and the COLUMN_DEFAULT column is a NULL value.
COLUMN_FLAGS	DBTYPE_UI4	A bitmask that describes column characteristics. The DBCOLUMNFLAGS enumerated type specifies the bits in the bitmask. For information about DBCOLUMNFLAGS, see IColumnsInfo::GetColumnInfo in the reference section. This column cannot contain a NULL value. If COLUMN_NAME refers to a column in a table or view that is updatable, one of either DBCOLUMNFLAGS_WRITE or DBCOLUMNFLAGS_WRITEUNKNOWN should be set. For more information about these flags, see "DBCOLUMNFLAGS Enumerated Type.
IS_NULLABLE	DBTYPE_BOOL	VARIANT_TRUE—The column might be nullable. VARIANT_FALSE—The column is known not to be nullable.
DATA_TYPE	DBTYPE_UI2	The indicator of the column's data type. If the data type of the column varies from row to row, this must be DBTYPE_VARIANT. This column cannot contain NULL. For a list of valid type indicators, see "Type Indicators" in Appendix A.
TYPE_GUID	DBTYPE_GUID	The GUID of the column's data type. Providers that do not use GUIDs to identify data types should return NULL in this column.
CHARACTER_MAXIMUM_LENGTH	DBTYPE_UI4	The maximum possible length of a value in the column. For character, binary, or bit columns, this is one of the following: The maximum length of the column in characters, bytes, or bits, respectively, if one is defined. For example, a CHAR(5) column in an SQL table has a maximum length of 5. The maximum length of the data type in characters, bytes, or bits, respectively, if the column does not have a defined length. Zero (0) if neither the column nor the data type has a defined maximum length. NULL for all other types of columns.
CHARACTER_OCTET_LENGTH	DBTYPE_UI4	Maximum length in octets (bytes) of the column, if the type of the column is character or binary. A value of zero means the column has no maximum length. NULL for all other types of columns.
NUMERIC_PRECISION	DBTYPE_UI2	If the column's data type is of a numeric data type other than VARNUMERIC, this is the maximum precision of the column. The precision of columns with a data type of DBTYPE_DECIMAL or DBTYPE_NUMERIC depends on the definition of the column. For the precision of all other numeric data types, see "Precision of Numeric Data Types" in Appendix A. If the column's data type is not numeric or is VARNUMERIC, this is NULL.
NUMERIC_SCALE	DBTYPE_I2	If the column's type indicator is DBTYPE_DECIMAL, DBTYPE_NUMERIC, or DBTYPE_VARNUMERIC, this is the number of digits to the right of the decimal point. Otherwise, this is NULL.
DATETIME_PRECISION	DBTYPE_UI4	Datetime precision (number of digits in the fractional seconds portion) of the column if the column is a datetime or interval type. If the column's data type is not datetime, this is NULL.
CHARACTER_SET_CATALOG	DBTYPE_WSTR	Catalog name in which the character set is defined. NULL if the provider does not support catalogs or different character sets.
CHARACTER_SET_SCHEMA	DBTYPE_WSTR	Unqualified schema name in which the character set is defined. NULL if the provider does not support schemas or different character sets.
CHARACTER_SET_NAME	DBTYPE_WSTR	Character set name. NULL if the provider does not support different character sets.
COLLATION_CATALOG	DBTYPE_WSTR	Catalog name in which the collation is defined. NULL if the provider does not support catalogs or different collations.
COLLATION_SCHEMA	DBTYPE_WSTR	Unqualified schema name in which the collation is defined. NULL if the provider does not support schemas or different collations.
COLLATION_NAME	DBTYPE_WSTR	Collation name. NULL if the provider does not support different collations.
DOMAIN_CATALOG	DBTYPE_WSTR	Catalog name in which the domain is defined. NULL if the provider does not support catalogs or domains.
DOMAIN_SCHEMA	DBTYPE_WSTR	Unqualified schema name in which the domain is defined. NULL if the provider does not support schemas or domains.
DOMAIN_NAME	DBTYPE_WSTR	Domain name. NULL if the provider does not support domains.
DESCRIPTION	DBTYPE_WSTR	Human-readable description of the column. For example, the description for a column named Name in the Employee table might be "Employee name." Null if there is no description associated with the column.