I went to jail the other day for DUI, judge told me I had no prior criminal history?

Typically in Washington State the court itself only has access to a person's Washington State criminal history through the Judicial Information System, which contains the criminal history for people in Washington State only. The prosecutor can obtain a NCIC, which is a national criminal history check that can reveal your AZ history. Unless the prosecutor obtains this information and provides it to the court, the court is unlikely to be aware of out of state history. This sounds like it was fortunate for you and hopefully the prosecutor does not run an NCIC. I hope this answers your question and good luck on your case.

It is likely the judge only checked DISCUS, which only contains Washngton State data. District or municipal judges don't have ready access to the NCIC nationwide system.

As the other answers stated: Basically, you lucked out. If and when the judge finds out, your conditions of release could change, and any recommendation from the prosecutor about your sentence could change as well.

Because judges typically only have access to your in state history at first appearance.

The judge may not have seen your criminal history because he or she may have been using a database that only had access to Washington criminal records. Be assured, however, that the judge will eventually become aware of your out-of-state criminal history though.