kdb+

How do we update a table column which is list type based on list indices range

How do we update a table column which is list type based on list indices range

sample table tab:([] date:2024.01.01+til 30;sym:30?`appl`msgt`googl;volume:30#(enlist 0.5+300?til 100));

Lets just work with row1 in current example so its easier

exec first volume from tab where i=0 //300

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Now, we want to query and update the table tab such that user passes start index and end index, take that and update the volume from tab to zero 0 for that index range.

We have 300 values in volume column for first row as eg. , say user passes start:100;end:200, so here we need to make the index 100 to 200 as zero in volume column where its is first row or any row given.

I tried to solve it by indexing a list but it works for single index but not works for a range of index in update statement

Solution

  • Using . amend

    q){[start;end] .[tab;(::;`volume;start+til end-start);:;0f]}[100;200]

    This will set indexes 100 to 200 as 0f in every volume row.