sqlColumns function

String sqlColumns(Iterable<String>? fields, [ String? shortcut ])

Converts a list of fields to a SQL fragment separated by comma.

Note: if fields is null, "*" is returned, i.e., all fields are assumed. if fields is empty, 1 is returned (so it is easier to construct a SQL statement).

Note: if a field starts with '(', or a number, we don't encode it with a double quotation. It is used to retrieve a constant, an expression, or anything you prefer not to encode.

For example, you can pass a field as ("assignee" is not null or "due" is null). Furthermore, you can name it (aka., virtual column or calculated column): ("assignee" is not null or "due" is null) alive

Here is an example of use:

access.query('select ${sqlColumns(fields)} from "Foo"');

• shortcut - the table shortcut to prefix the field (column name). If specified, the result will be T."field1",T."field2" if shortcut is T. Note: shortcut is case insensitive.

Implementation

String sqlColumns(Iterable<String>? fields, [String? shortcut]) {
  if (fields == null)
    return "*";
  if (fields.isEmpty)
    return '1';

  assert(fields is Set || fields.toSet().length == fields.length, "Dup? $fields");

  final sql = StringBuffer();
  bool first = true;
  for (final field in fields) {
    if (first) first = false;
    else sql.write(',');

    if (_reExpr.hasMatch(field)) {
      sql.write(field);
    } else {
      if (shortcut != null)
        sql..write(shortcut)..write('.');
      sql..write('"')..write(field)..write('"');
    }
  }
  return sql.toString();
}