title: Pandas read sql integer became float
body: <p>I met a problem that when I use pandas to read Mysql table, some columns (see 'to_nlc') used to be integer became a float number (automatically add .0 after that).
  Can anyone figure it out? Or some guessings? Thanks very much!</p>
  
  <p><a href="https://i.stack.imgur.com/1obo8.png" rel="noreferrer"><img src="https://i.stack.imgur.com/1obo8.png" alt="enter image description here"></a>
  <a href="https://i.stack.imgur.com/vexAh.png" rel="noreferrer"><img src="https://i.stack.imgur.com/vexAh.png" alt="enter image description here"></a><a href="https://i.stack.imgur.com/oCNJg.png" rel="noreferrer"><img src="https://i.stack.imgur.com/oCNJg.png" alt="enter image description here"></a></p>