• Is bo_Live5.dbo.BLT_BILLM the only table in your FROMlist which has sets of rows having the same value of MATTER_UNO/matter_name?

    Are you expecting, in your output, only one row per matter_name?

    “Write the query the simplest way. If through testing it becomes clear that the performance is inadequate, consider alternative query forms.” - Gail Shaw

    For fast, accurate and documented assistance in answering your questions, please read this article.
    Understanding and using APPLY, (I) and (II) Paul White
    Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden