Ruby on rails Ruby DBI：如何在使用method时添加execute参数；在（？）中；

以下是我使用DBI的示例代码：

begin
  dbh = DBI.connect("DBI:Mysql:Test:localhost", "testuser", "testpassword")

  sql = "select u.email, u.account_name, u.height, u.weight 
         from test_users 
         where id in (?)
         group by u.id
         order by u.id
         into outfile '/tmp/test.csv'
         fields terminated by ','
         enclosed by '\"'
         lines terminated by '\n'"

  sth = dbh.prepare(sql)
  sth.execute('1,2,3')
  sth.finish
rescue DBI::DatabaseError => e
  puts "An error occurred"
  puts "Error code:    #{e.err}"
  puts "Error message: #{e.errstr}"
ensure
  # disconnect from server
  dbh.disconnect if dbh
end

但是它给我的sql，比如“in”方法的值是不正确的：

  select u.email, u.account_name, u.height, u.weight 
  from test_users 
  where id in ('1,2,3')
  group by u.id
  order by u.id
  into outfile '/tmp/test.csv'
  fields terminated by ','
  enclosed by '\"'
  lines terminated by '\n'"

我希望这样（注意更改结果是：“id in（1,2,3）”）：

---

IN子句不是这样工作的，您需要有与参数数量相同的

？

，在您的情况下，您应该有：

sql = "select u.email, u.account_name, u.height, u.weight 
         from test_users 
         where id in (?,?,?)
         group by u.id
         order by u.id
         into outfile '/tmp/test.csv'
         fields terminated by ','
         enclosed by '\"'
         lines terminated by '\n'"

---

然后将每个值传递给查询。

更一般地说，您可以使用

map

和

join

生成占位符：

foo = 'foo'
bar_array = [1, 2, 3]
bar_placeholders = bar_array.map { '?' }.join(', ')
baz = 18
sql = <<-SQL
  SELECT * FROM t
  WHERE foo = ?
  AND bar IN (#{bar_placeholders})
  AND baz > ?
SQL
...
sth.execute(foo, *bar_array, baz)

foo='foo'
bar_数组=[1,2,3]
bar_占位符=bar_array.map{'？'}.join（'，'））
baz=18
sql=您是否在数组中尝试过它
（[1,2,3]）
@PraveshKhatri我尝试过，它给我的结果是：“[1,2,3]”我只是在查看sql，而没有查看结果。实际上前面的代码也是正确的。虽然sql看起来不友好，但select结果是正确的。谢谢你的回答，我学到了很多。
foo = 'foo'
bar_array = [1, 2, 3]
bar_placeholders = bar_array.map { '?' }.join(', ')
baz = 18
sql = <<-SQL
  SELECT * FROM t
  WHERE foo = ?
  AND bar IN (#{bar_placeholders})
  AND baz > ?
SQL
...
sth.execute(foo, *bar_array, baz)