# File lib/sequel/extensions/string_agg.rb, line 86
 86:         def string_agg_sql_append(sql, sa)
 87:           if defined?(super)
 88:             return super
 89:           end
 90: 
 91:           expr = sa.expr
 92:           separator = sa.separator || ","
 93:           order = sa.order_expr
 94:           distinct = sa.is_distinct?
 95: 
 96:           case db_type = db.database_type
 97:           when :postgres, :sqlanywhere
 98:             f = Function.new(db_type == :postgres ? :string_agg : :list, expr, separator)
 99:             if order
100:               f = f.order(*order)
101:             end
102:             if distinct
103:               f = f.distinct
104:             end
105:             literal_append(sql, f)
106:           when :mysql, :hsqldb, :h2
107:             sql << "GROUP_CONCAT("
108:             if distinct
109:               sql << "DISTINCT "
110:             end
111:             literal_append(sql, expr)
112:             if order
113:               sql << " ORDER BY "
114:               expression_list_append(sql, order)
115:             end
116:             sql << " SEPARATOR "
117:             literal_append(sql, separator)
118:             sql << ")"
119:           when :oracle, :db2
120:             if distinct
121:               raise Error, "string_agg with distinct is not implemented on #{db.database_type}"
122:             end
123:             literal_append(sql, Function.new(:listagg, expr, separator))
124:             if order
125:               sql << " WITHIN GROUP (ORDER BY "
126:               expression_list_append(sql, order)
127:               sql << ")"
128:             else
129:               sql << " WITHIN GROUP (ORDER BY 1)"
130:             end
131:           else
132:             raise Error, "string_agg is not implemented on #{db.database_type}"
133:           end
134:         end