Just so I understand the requirement, if you have the below table:
col_a, col_b, col_c
val1,val2,val3
val4,val5,val6
…
And you want to add a new column with records from the others, like so:
col_a, col_b, col_c, col_new
val1,val2,val3, {col_a: val1, col_b: val2, col_c: val3}
val4,val5,val6, {col_a: val4, col_b: val5, col_c: val6}
…
Is this correct?