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NAME: dbtxptr
FUNCTION:
Return the value of the text pointer for a column in the current
row.
SYNTAX:
DBBINARY *dbtxptr(dbproc, column)
DBPROCESS *dbproc;
int column;
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COMMENTS:
o Every database column row of type SYBTEXT or SYBIMAGE has an
associated text pointer, which uniquely identifies the text or
image value. This text pointer is used by the dbwritetext()
function to update text and image values.
o It's important that all the rows of the specified text or image
column have valid text pointers. A text or image column row
will have a valid text pointer if it contains data. However,
if the text or image column row contains a null value, its text
pointer will be valid only if the null value was explicitly
entered with the UPDATE statement.
Assume a table textnull with columns key and x, where x is a
text column that permits nulls. The following statement
assigns valid text pointers to the text column's rows:
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update textnull
set x = null
On the other hand, the INSERT of a null value into a text
column does not provide a valid text pointer. This is true for
an INSERT of an explicit null or an INSERT of an implicit null,
such as the following:
insert textnull (key)
values (2)
When dealing with a null text or image value, be sure to use
UPDATE to get a valid text pointer.
o For an example that uses dbtxptr(), see the dbwritetext()
manual page.
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PARAMETERS:
dbproc - A pointer to the DBPROCESS structure that provides the
connection for a particular front-end/SQL Server process. It
contains all the information that DB-Library uses to manage
communications and data between the front end and SQL Server.
column - The number of the column of interest. The first column
in a table is number 1.
RETURNS:
A DBBINARY pointer to the text pointer for the column of
interest. This pointer may be NULL.
SEE ALSO:
dbtxtimestamp, dbwritetext