<h3>Return specific columns ("Filter" operator is optional):</h3>
<li>[:, "colname1"], [: "colname2"]</li>
<li>filter:[:, "colname1"], [: "colname2"]</li>

<p>Can also slice by column number: <b>[:, 1], [:,3]</b>. For single slice, brackets can be left out: <b>:,1</b></p>

<h3>Return column "colname3" for rows where value of column "colname1" is between "minval1" and "maxval1" and value of column "colname2" is between "minval2" and "maxval2":</h3>
<li>:,"colname3" { [:,"colname1"] > minval1 and [:,"colname1