Vaughan Roberts, 30, of Rhos-on-Sea, Conwy, accepted a £1,800 loan from the same man, Caernarfon Crown Court was told.
Judge Merfyn Hughes QC told Roberts, who had denied the charges, he had brought disgrace on North Wales Police.
The judge also said he had been shocked by the conduct of other officers.
Roberts was convicted of obtaining and disclosing data relating to doorman Peter Lewis.
The detective constable had also received a loan from Mr Lewis, who was an alleged suspect, the jury heard.
Roberts said he was accessing the database to get Mr Lewis’ home phone number because he had been told he was spreading untrue rumours that he and other officers were using steroids.
Judge Hughes said Roberts should not have become friendly with Mr Lewis, adding the defendant had been arrogant and conceited concerning the offences and in his evidence.
‘Bump up their figures’
Roberts, who earns up to £36,000 a year, had told lies, the judge said.
“The fact that you may lose your job is of course no mitigation,” the judge added.
The offences carry a monetary penalty and Roberts will be sentenced next week.
During the case, the court heard that some police officers would pass on intelligence from informants to each other to log on the police computer, so that they could “bump up their figures”.
Judge Merfyn Hughes told Caernarfon Crown Court: “Quite frankly I was shocked, and it undermines the trust which we all have in the police force.”
However, he accepted that such conduct was exceptional.
He also suggested that a police constable, who gave evidence on behalf of Roberts, should be the subject of an internal inquiry.
North Wales Police said it would not comment on the case until after Roberts had been sentenced.