Write update query in power query

where run_datetime is between start_rundatetime and end_rundatetime.

There is no end_rundatetime column in your sample data. Please provide sample data that fully covers your issue.
Please show the expected outcome based on the sample data you provided.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("dY49CoAwDEbv0tnClx9tMyriWgcHQbz/NYyKg2gDgUfgkbdtATYZqB8jBrWouU+hCfBlsCKxOFIHnwtatBT2puLRj3feRHJd4o8kYhdoovsZobi3LpFYNOpc8itSTnwa2eoKVRSv2w8=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [job_id = _t, step_id = _t, run_date = _t, run_time = _t, duration = _t]),
    #"Grouped Rows" = Table.Group(Source, {"job_id"}, {{"Rows", each _, type table [job_id=nullable text, step_id=nullable text, run_date=nullable text, run_time=nullable text, duration=nullable text]}, {"schedule_id", each List.Min([run_date])&List.Min([run_time]), type nullable text}}),
    #"Expanded Rows" = Table.ExpandTableColumn(#"Grouped Rows", "Rows", {"step_id", "run_date", "run_time", "duration"}, {"step_id", "run_date", "run_time", "duration"})
in
    #"Expanded Rows"

How to use this code: Create a new Blank Query. Click on "Advanced Editor". Replace the code in the window with the code provided here. Click "Done". Once you examined the code, replace the Source step with your own source.

Hi Anonymous, check this:

Output

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("dY49CoAwDEbv0tnClx9tMyriWgcHQbz/NYyKg2gDgUfgkbdtATYZqB8jBrWouU+hCfBlsCKxOFIHnwtatBT2puLRj3feRHJd4o8kYhdoovsZobi3LpFYNOpc8itSTnwa2eoKVRSv2w8=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [job_id = _t, step_id = _t, run_date = _t, run_time = _t, duration = _t]),
    ChangedType = Table.TransformColumnTypes(Source,{{"step_id", Int64.Type}, {"run_date", Int64.Type}, {"run_time", Int64.Type}, {"duration", Int64.Type}}),
    GroupedRows = Table.Group(ChangedType, {"job_id"}, {{"All", each 
        [ a = Table.SelectRows(_, (x)=> x[step_id] = 0){0}?,
          b = Table.AddColumn(_, "schedule_id", (x)=> Text.From(a[run_date]?) & Text.From(a[run_time]?), type text)
        ][b], type table}}),
    Combined = Table.Combine(GroupedRows[All])
in
    Combined