title: Python - Pandasql - IIf Function doesn't work Error
body: <p>Trying to execute the following code:</p>
  
  <pre><code>import pandas as pd
  import pandasql as ps
  
  df = pd.DataFrame({'A':[5,6,7], 'B':[7,8,9]})
  print(df)
  
         A  B
      0  5  7
      1  6  8
      2  7  9
  
  qry = """SELECT df.*, IIf(A Is Null,[B],[A]) AS NEW_A FROM df;"""
  df1 = ps.sqldf(qry, globals())
  print(df1)
  </code></pre>
  
  <p>yields this error:</p>
  
  <pre><code>PandaSQLException: (sqlite3.OperationalError) no such function: IIf 
  [SQL: 'SELECT df.*, IIf(A Is Null,[B],[A]) AS NEW_A FROM df;']
  </code></pre>
  
  <p>I've tried various combinations of different syntax regarding square brackets, globals/locals etc. but couldn't find the issue. Is this function simply not existing? </p>
  
  <p>I simply copied the SQL query from an MS Access query but for other cases this works fine.</p>