Error when loading CZML

I linked sql in cjs file and sent czml file to js file by ajax.

And I proceeded with dataSource.load(czml),

“DeveloperError {name: ‘DeveloperError’, message: ‘czml is required.’”

The error appears like this: Any workaround?
Thank you so much for your help.

Hi there,

In the line dataSource.load(czml), the czml variable is likely undefined or null.