Databases Reference
In-Depth Information
Clicking on
Go
gives these results (shown partially in the following screenshot):
This is a standard results page. If the results ran in pages, we could navigate
through them, and edit and delete data for the subset we have chosen during the
process. Another feature of phpMyAdmin is that the columns used as the criteria
are highlighted by changing the border color of the columns to better reflect their
importance on the results page.
It isn't necessary to specify that the
isbn
column be displayed even though this is
the column in which we search. We could have selected only the
title
column for
display (refer to the
Selecting
the
columns
to
be
displayed
section) and chosen the
isbn
column as a criterion.
Searching for empty / non-empty values
Two handy operators are present in the operator's list when the column has a
character type such as
CHAR
,
VARCHAR
, or
TEXT
:
•
=
''
•
!=
''
Those are the ones to use when you want to search for an empty (
=
''
) or not empty
(
!=
''
) value in some column. Normally, typing nothing in a column's
Value
field
means that this column does not participate in the search process. However, with
one of these operators, this column is included in the generated search query.
Please do not confuse this method with searching for a
NULL
value, which is quite different. Indeed, a
NULL
value (refer to
http://en.wikipedia.org/wiki/Null_(SQL)
for a more
complete explanation) is a special value that conveys that some
information is missing in this column.
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