What Is a DDL File?

How to Open, Edit, & Convert DDL Files

Screenshot of several DDL files in Windows 10 that open with Notepad
DDL Files.

A file with the DDL file extension is an SQL Data Definition Language file. These are plain text files that contain commands used to describe the structure of a database, like its tables, records, columns, and other fields.

For example, given that certain syntax rules are followed, a DDL file might utilize the CREATE command to build domains, character sets, and tables. Other command examples include DROP, RENAME, and ALTER.

Note: The term DDL is also used in the general sense to describe any language that refers to data or data structures, so not every data definition language file uses the .DDL file extension. In fact, plenty of SQL Data Definition Language files end in .SQL.

How to Open a DDL File

DDL files can be opened with EclipseLink or IntelliJ IDEA. Another way to open a DDL file is with an application that supports reading text files, like the ones we've hand-picked in this Best Free Text Editors list.

Note: On the IntelliJ IDEA download page are two links for the Windows, macOS, and Linux program. One download will give you the Ultimate edition and the other is for the Community edition. Both can open and edit DDL files but only the Community option is open-source and free; the other is free only during the trial period.

Tip: If you find that an application on your PC does try to open the DDL file but it's the wrong application or if you would rather have another installed program open DDL files, see our How to Change the Default Program for a Specific File Extension guide for making that change in Windows.

How to Convert a DDL File

Most file types can be converted using a free file converter, but I don't know of any specific ones that can convert files that end with .DDL. Because this file extension appears to be pretty uncommon, it's unlikely that there are many options for converting DDL files to different formats.

However, one thing you can try is opening the DDL file with one of the file openers above, and then using that program's File or Export menu to save the file to a different format. Most programs support this type of conversion, so there's a good chance that the ones linked above do, too.

Another option is to use the free online Code Beautify converter. It can convert lots of text-based formats to other similar file formats, so it might prove useful in converting the text within a DDL file to some other format. If it works, just copy the output text from the conversion and paste it into a text editor so that you can save it with the appropriate file extension.

Although I'm not completely sure how practical this type of conversion is, IBM has this Splitting DDL tutorial that might be useful if you're using the DDL file with IBM Redbooks.

Is Your File Still Not Opening?

A likely reason for why you can't open your file even after trying the DDL openers above, is because you're confusing a different file for one that uses the .DDL file extension. Some file extensions look awfully similar, but that doesn't mean that their file formats are related.

For example, you can see how easy it'd be to confuse a DLL file for a DDL file even though they don't open with the same programs or use the same format. If you're really dealing with a DLL file, you'll most definitely get an error or unexpected results if you attempt to open one with a DDL file opener, and vice versa.

The same is true for DDD files. These are either Alpha Five Data Dictionary files or GLBasic 3D Data files, but neither of those formats have anything to do with SQL Data Definition Language files. Just like with DLL files, you need an entirely separate program to open them.

If you don't really have a DDL file, then research the file extension that is attached to the end of your file. That way, you can find out what format it's in and which software programs are compatible with that specific file.

More Help With DDL Files

If you do have a DDL file but it's not opening or working properly, see Get More Help for information about contacting me on social networks or via email, posting on tech support forums, and more. Let me know what kinds of problems you're having with opening or using the DDL file and I'll see what I can do to help.