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Generic SQL Table Export

Generic SQL Table Export

In my last article (CFDJ, Vol. 1, issue 6) I presented Array_Table, a universal browser-based table viewer and query engine. Array_Table allows you to browse, edit and query any Microsoft SQL Server table. It's 100% dynamic so it works with any database.

Many readers and clients loved the new capability and ease it offered. And they wanted more, of course.

Feeling Trapped?
Most data-driven Web sites are located on remote servers. If you use a server-based database like Microsoft SQL Server, it's difficult to retrieve table data locally. Downloading entire tables for use with your desktop software or to keep a local backup seems impossible. In addition, your end users may periodically need to download data from the data-driven sites you create.

Freedom At Last!
We're going to add generic table export capability to Array_Table. It'll allow you to generate a common, popular and generic text file that can be used in almost any desktop application or database. Array_Export will create a text file and optionally e-mail it to you. With this functionality you'll have the freedom to actually get to your data. You can see Array_Table and Array_Export in action at www. arrayone.com/Table/.Do_it! To present your users with a list of available tables, I created Table_List.cfm (see Figure 1).

This form shows you a list of all the tables in a data source with the option to view the data or query the table. I've added a choice, "Export", to the table list. This is the only necessary addition to Table_List.cfm (see Listing 1) and it's simply a hot link to the table export program. Here's the code.... <a href="Export/Export_Menu.cfm?TableName=#Table_List.Name#">Export</a>

All of the export files are being stored and called from a subfolder, "Export". This keeps your files neat and provides one point of reference if you have to modify any export-related code.

When you click on "Export", the Export_menu.cfm script is called and you're presented with the export menu (see Figure 2 and Listing 2).

The table you selected is automatically passed to the export menu. Now you have the option of exporting the data to a comma- or tab-delimited file, with or without field names in the file header.

If you enter your e-mail address, Array_Export will e-mail the exported data file to you.

How'd He Do That?
It's easier than you think. Array_Export.cfm calls Export.Cfm (see Listing 3). Export.Cfm passes the tablename along with your export selections from the menu to the main ColdFusion script, Table_Export.cfm (see Listing 4). This script handles all the export functionality. Let's examine Export.Cfm.

<!--- Export.CFM - Passes logon and user choice parameters to the export engine, Table_Export.CFM. --->
<!--- Set export file name --->
<cfset Dir_Name = #getdirectory
frompath(gettemplatepath())#>
<cfset FileName = "#Dir_Name#\Data\#TableName##DateFormat("#Now()#","mmddyyyy")#.txt">
<!--- Call export engine --->
<cf_Table_Export
DSN="Demo"
Username="Guest"
Password="Guest"
Table="#TableName#"
FileName="#FileName#"
Delimiter="#Form.Delimiter#"
ColumnHeader="#Form.ColumnHeader#"
Email="#Form.Email#">

Export.cfm sets the directory where the exported data file will be stored. Then it sets the name of the exported file to be the file name plus the current date. So if you were exporting a table called "Sales" on December 6, 1999, the exported file name would be "Sales12061999.txt". Export.cfm then calls Table_Export.

cfm and passes all the necessary parameters, such as tablename and filename.

Table_Export.Cfm There are four steps in exporting the table:

1. Query the table to retrieve all of the rows. 3. Write the data out to a text file in delimited text.
4. Mail the exported file to the user.
Step 1. Query the table.

<cfquery name="Export" datasource="Demo" username="Guest" password="Guest">
Select * from #Attributes.Table#
</cfquery>
<cfif Export.RecordCount EQ 0>
There are no records to export
<cfabort>
</cfif>

Simply query the table for all records. If there are none, display a message to the user and abort. If there are, we go to the second step.

Step 2. Get a list of all fields.

<cfquery name="Field_List" datasource="Demo" username="Guest" password="Guest">
SELECT syscolumns.Name
FROM sysobjects , syscolumns
WHERE syscolumns.id = sysobjects.ID
AND upper(sysobjects.Name) = '#Attributes.Table#'
</cfquery>
<!--- Put field list into an array --->
<cfset x = "">
<cfloop query="Field_List">
<cfset x = x & Field_List.Name>
<cfif Field_List.CurrentRow NEQ Field_List.RecordCount>
<cfset x = x & Attributes.Delimiter>
</cfif>
</cfloop>

Here we query the SQL Server system tables (see December 1999 article) to retrieve the list of fieldnames in the table. We need the field list so we can export the data and separate it by fields. The variable x will hold the list of fields, each fieldname separated by a comma.

<Cffile> is the perfect tag for creating and editing text files. Using the action="write" option, ColdFusion will create the text file if it doesn't already exist.

<!--- Create export file --->
<cffile action="WRITE" file="#Attri-butes.FileName#" output=""
addnewline="No">

Once the file is created, you can write the field list header to it (if the user chose to add fieldnames to the file).

<cffile action="APPEND" file="#Attributes.FileName#" output="#x##Chr(13)##Chr(10)#" addnewline="No">

Here, the variable x, which now holds the list of fields, is used.

Step 3. Write the data out to a text file in delimited text.

To make it easier to loop through the list of fields, I prefer to use arrays. The following command converts the fieldlist to an array called FL.

<cfset FL = ListToArray(x, #Attributes. Delimiter#)>

A simple nested (double) loop can now be used to loop through all the records in the table and output all the data. During the loop a single line of data is created in the variable D. It contains all data from all fields as well as the field delimiter character. After the data line is built, it can be written to the text file using <cffile> with the action="append". Append adds new lines to the file without erasing any existing data.

<!--- Loop through the export query which contains all data rows --->
<cfloop query="Export">
<cfset d = "">
<!--- Now loop through the field list and build the row export data --->
<cfloop index="n" from="1" to="#ArrayLen(FL)#">
<cfset S = SetVariable("S", "#FL[n]#")>
<cfset d = d & Trim(#Evaluate(S)#)>
<cfif n NEQ ArrayLen(FL)>
<cfset d = d & Attributes.Delimiter>
</cfif>
</cfloop>
<!--- Write record to text file --->
<cffile action="APPEND" file="#Attributes.FileName#"
input="#d##Chr(13)##Chr(10)#"
addnewline="no">
</cfloop>

Step 4. Mail the exported file to the user.

After the export loop completes the file, a new export file will be sitting on the server. If the user entered an e-mail address on the Export_menu.cfm form, the file will automatically be e-mailed to them. It doesn't get any easier than this.

Extension Cord, Please
Now you have a scalable, dynamic tool to view, query and export data from any table. With the new data export capability it's easy to bring data back to your desktop for backup or manipulation. Since the export generates pure text files, the data can be used in virtually any application. The possibilities are still endless.

More Stories By David Schwartz

David Schwartz is the president of Array Software Inc., a New Jersey-based software company. Array creates global data-driven Internet and intranet Web sites using ColdFusion, Oracle, MS SQL Server and Java. David has been developing turnkey custom database software for 14 years.

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