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Transcript
Objects in Access General Access objects Data access objects (DAO) used for data management data definition data manipulation used only in code modules Commonly Used Data Access Objects DAO Description Container Database Object that contains information about other objects The open database DBEngine The database engine Property An object property QueryDef A saved query Commonly Used Data Access Objects DAO Description Recordset Set of records defined by a table or query Relation Relationship between 2 tables or queries Tabledef A saved table User A user account in the database engine Workspace An active database session Using DAO Using the current database declare an object variable of type Database use the CurrentDb function to store a reference to the current database example Dim dbs As Database Set dbs = CurrentDb( ) Using DAO Looping through collections uses For Each statement, similar to a For Next loop example Dim dbs As Database Dim conTest As Container Set dbs = CurrentDb() For Each conTest In dbs.Containers Debug.Print “Container: “; conTest.Name Next Using DAO Recordsets records belonging to a table or query most commonly used types table-type dynaset-type snapshot-type Using DAO Table-type recordsets default type for any recordset object can use indexes to speed up the process of searching for records example Dim rec As Recordset Set rec = db.OpenRecordset(“Students”) Using DAO Dynaset-type recordsets can contain a table or the result of a query can be edited and the results will be reflected in the underlying tables useful if the recordset object is very large example Set rec = db.OpenRecordset(“Students”, dbOpenDynaset) Using DAO Snapshot-type not updateable example Set rec = db.OpenRecordset(“Students”, dbOpenSnapshot) Using DAO Moving through recordsets Method Description rec.MoveNext Makes next record current record MovePrevious Makes previous record current record MoveFirst Makes first record current record MoveLast Makes last record current record Move n Makes n records away the current record Using DAO RecordsetClone method alternative to OpenRecordset method creates copy of recordset that can be manipulated independently of the form’s recordset Bookmark property what Access uses instead of record numbers stored as an array of bytes used to synchronize recordset objects which are clones of each other Using DAO Finding records in table-type recordsets Seek method used with indexed fields select indexed field to search on specify search criteria example rec.Index = “Price” rec.Seek “=“, curPrice Using DAO Finding records in dynasets and snapshots Find method Works on non-indexed fields for all types of recordsets Four methods FindFirst FindLast FindNext FindPrevious Using DAO Methods to edit recordsets Method Edit Description Copies current record to copy buffer to allow editing AddNew Creates a new record in the copy buffer with default values (if any) Update Saves any changes made to the record in the copy buffer CancelUpdate Empties the copy buffer without saving any changes Delete Deletes the current record Using DAO Editing field values in a recordset example rec.Edit rec!strField = NewValue rec.Update Using DAO With … End With logic structure often used with DAOs, but can be used with controls and collections