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Introduction |
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Using SQL Blob Export |
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Tags
When
naming files, you use tags as placeholders for system and column
values.
System values
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There
are 2 system values you can use, the current row number, and the
column number. Row numbers are indicated by the
<%row%> tag, and column number by the
<%columm%> tag e.g.
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You
can add format specifiers to both these system values as they are
numeric values. See below for details.
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Database column values
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To use
a value from a table or query column, enter the name of the column
enclosed in angled brackets. For e.g. if you had the following
result set:
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and
you wanted to name the exported files using the
LargePhotoFileName value, simply enter the column name
enclosed in angled brackets i.e.
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Conditional specifier
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You
can also choose to use a tag only for specific columns. Say we have
the following result set:
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We
want to use the ThumbnailPhotoFileName column value when we
export column 2, and the LargePhotoFileName column value
when we export column 4. To do that, we add a conditional column
tag to the end of the column tag e.g.
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A
conditional specifier can be used for system value tags and column
value tags. It comes after any format specifiers, and is preceded
by a : followed by the index of the blob data column that uses this
value. In the example above, we had the following values:
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<ThumbnailPhotoFileName::2><LargePhotoFileName:4>
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which
means that use the value from ThumbnailPhotoFileName (with
no format specifiers) when we are exporting blob data from column 2
in our result set, and use the value from LargePhotoFileName
(again with no format specifiers) when we are exporting blob data
from the 4th column in our result set.
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Another
example, the following value:
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means
that we use the value from the ID column, is formatted to 4
digits, and is only used when we are exporting blob data from
column 2 in our result set.
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Format specifiers
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For
file names, you can use the FILENAME format specifier to
extract only the file name portion from a fully qualified file
name. For e.g. the LargeImageFileName column below stores
fully qualified file names:
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Using
the <LargePhotoFileName> tag results in errors when
SQL Blob Export tries to generate the file names:
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To
address this, we append the FILENAME format specifier to the
tag e.g.
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SQL
Blob Export now only uses the file name portion of the column value
to generate file names i.e.
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For
numeric values, you can also use a format specifier. E.g. the
<%row%> tag is a sequential number of each image that
is exported. Using the tag without a format specifier will result
in the following values: 1, 2, 3, ... (n). If you want to format
the sequence value to 4 digits, prefixed with 0s, you can amend the
tag to include the format specified this way:
<%row:0000%>. This will then result in the following
values: 0001, 0002, 0003, ... (n).
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For
datetime values retrieved from a database column, you can also use
format specifiers to determine how to display the datetime value.
The default format is yyyymmdd, so for a datetime value of 31
January 1970, the displayed value is 19700131. See this page for details of the
available datetime format specifiers.
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