Teach Yourself Borland C++ in 14 Days - portal

456 Day 12
NOTE
For server tables, the SQL must
■ Use Local SQL syntax only
■ Involve only one table
■ Not contain aggregate functions
The TLiveQuery component that you can obtain at http://
www.mcp.com/sams/codecenter.html provides an alternative method
of acquiring updatable result sets from database servers. Basically, it
creates and opens a temporary view on your server that you may then
update as though it were a table. The updates you can make to this
“live” result set are limited only by the restrictions your server places
on updatable views.
The First method moves to the top of the TDataset, and the Last method moves to the
bottom. The Prior and Next methods move to the previous and next rows, respectively. You
use the MoveBy method to move a number of rows forward or backward from the current row.
Use the Bof property to determine whether the TDataset cursor is at its beginning. Use the
Eof property to determine whether the cursor has reached the TDataset’s end. These two
properties can be useful in looping through the rows in a TDataset.
WARNING
Be careful that you don’t make bad assumptions about the Bof and Eof
properties. You can’t assume that Bof will be true just because you’re
on the first row of a query result set, nor can you assume that Eof will
be true when you’re on the last row of a result set. Typically, an
additional Prior or Next is required to set Bof or Eof to true. For
example, the sequence First, Next, Prior won’t reset Bof to true, but
First, Next, Prior, Prior will. Note that Bof is true immediately after
you open a query or call the First method, and Eof is true immediately
after you call the Last method.
The Append and Insert methods are used to add blank rows to a TDataset. Append adds a
record to the end of the TDataset, whereas Insert adds it at the current cursor position. Along
these same lines, the AppendRecord and InsertRecord methods are used to add non-blank
rows to a TDataset using a supplied set of field values.