• You might need an input style for CONVERT:

    ;WITH Sampledata AS (

    SELECT lastrundate = CAST(20130620 AS INT)

    )

    SELECT

    lastrundate_INT = lastrundate,

    lastrundate_CHAR8 = CAST(lastrundate AS CHAR(8)),

    lastrundate_DATE = CONVERT(DATE, CAST(lastrundate AS CHAR(8)),112)

    FROM Sampledata

    “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