Explain EXPLAIN SYNTAX (children 2)
 Set
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 3)
    ExpressionList (children 1)
     Function count (children 1)
      ExpressionList
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       TableIdentifier tab
    Function like (children 1)
     ExpressionList (children 2)
      Identifier col_lowcardinality_nullable_string
      Literal \'a%\'
