CLIO, the online library catalog, contains records for almost all Chinese-language materials, including books, periodicals, microforms, and databases.
When searching CLIO, the Chinese romanization system one should use is Library of Congress Pinyin, which is based on China's Pinyin system but has significant exceptions.
You may look at the examples listed in Library of Congress New Chinese Romanization Guidelines to quickly understand the exceptions.
You may use Chinese characters for searching Chinese language materials in CLIO, but Chinese romanization will yield the best search results, hence using Chinese characters is not recommended.
However, most CLIO records are included in WorldCat. WorldCat can be searched by using either Library of Congress Pinyin or preferably, Chinese characters, either traditional or simplified, to see the holding status at Columbia and elsewhere. Many researchers simply search WorldCat first. Please note that not all library materials of Columbia one may find in CLIO are available in Worldcat. Most materials available in CLIO are in WorldCat though.