CreateQuery alter_table (children 3)
 Identifier alter_table
 Columns definition (children 1)
  ExpressionList (children 2)
   ColumnDeclaration a (children 1)
    DataType UInt8
   ColumnDeclaration b (children 1)
    DataType Int16
 Storage definition (children 2)
  Function MergeTree
  Identifier a
