CDaoRecordset::Seek

Статья
10/16/2008

Call this member function to locate the record in an indexed table-type recordset object that satisfies the specified criteria for the current index and make that record the current record.

BOOL Seek(
   LPCTSTR lpszComparison,
   COleVariant* pKey1,
   COleVariant* pKey2 = NULL,
   COleVariant* pKey3 = NULL 
);
BOOL Seek(
   LPCTSTR lpszComparison,
   COleVariant* pKeyArray,
   WORD nKeys 
);

Параметры

lpszComparison
One of the following string expressions: "<", "<=", "=", ">=", or ">".
pKey1
A pointer to a COleVariant whose value corresponds to the first field in the index. Required.
pKey2
A pointer to a COleVariant whose value corresponds to the second field in the index, if any. Defaults to NULL.
pKey3
A pointer to a COleVariant whose value corresponds to the third field in the index, if any. Defaults to NULL.
pKeyArray
A pointer to an array of variants. The array size corresponds to the number of fields in the index.
nKeys
An integer corresponding to the size of the array, which is the number of fields in the index.

Примечание.

Do not specify wildcards in the keys. Wildcards will cause Seek to return no matching records.

Примечание.
Do not specify wildcards in the keys. Wildcards will cause Seek to return no matching records.

Возвращаемое значение

Nonzero if matching records are found, otherwise 0.

Заметки

Use the second (array) version of Seek to handle indexes of four fields or more.

Seek enables high-performance index searching on table-type recordsets. You must set the current index by calling SetCurrentIndex before calling Seek. If the index identifies a nonunique key field or fields, Seek locates the first record that satisfies the criteria. If you do not set an index, an exception is thrown.

Note that if you are not creating a UNICODE recordset, the COleVariant objects must be explicitly declared ANSI. This can be done by using the COleVariant::COleVariant( lpszSrc**,** vtSrc ) form of constructor with vtSrc set to VT_BSTRT (ANSI) or by using the COleVariant function SetString( lpszSrc**,** vtSrc ) with vtSrc set to VT_BSTRT.

When you call Seek, you pass one or more key values and a comparison operator ("<", "<=", "=", ">=", or ">"). Seek searches through the specified key fields and locates the first record that satisfies the criteria specified by lpszComparison and pKey1. Once found, Seek returns nonzero, and makes that record current. If Seek fails to locate a match, Seek returns zero, and the current record is undefined. When using DAO directly, you must explicitly check the NoMatch property.

If lpszComparison is "=", ">=", or ">", Seek starts at the beginning of the index. If lpszComparison is "<" or "<=", Seek starts at the end of the index and searches backward unless there are duplicate index entries at the end. In this case, Seek starts at an arbitrary entry among the duplicate index entries at the end of the index.

There does not have to be a current record when you use Seek.

To locate a record in a dynaset-type or snapshot-type recordset that satisfies a specific condition, use the Find operations. To include all records, not just those that satisfy a specific condition, use the Move operations to move from record to record.

You cannot call Seek on an attached table of any type because attached tables must be opened as dynaset-type or snapshot-type recordsets. However, if you call CDaoDatabase::Open to directly open an installable ISAM database, you can call Seek on tables in that database, although the performance may be slow.

For related information, see the topic "Seek Method" in DAO Help.