How to extract a column (or a row) of a matrix as another column vector/ column matrix (or a row vector), not as a list?

a = mat[[All, {1}]]

{{Subscript[m, 1, 1]}, {Subscript[m, 2, 1]}, {Subscript[m, 3, 1]},
  {Subscript[m, 4, 1]}, {Subscript[m, 5, 1]}}

MatrixForm  @ a

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Try Partition[mat[[All, 1]], 1].

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