mysql - 当提供另一列的值时，选择小于当前 id 的记录

Question

如何选择小于提供的哈希值 id 的记录？这甚至可能吗？我从 php 获取 hashKey 值，并基于此，需要选择小于包含该 hashKey 的行的 id 的记录。

在伪代码中：

@thisHash = '08d448b86a3b2f7d05a721ef18a8f02f';
select id from myTable where id < {id belonging to @thisHash}; 

表数据

"id"    "country"   "hashKey"
"1"     "US"        "319f64ab2c62ee50cc9571f22e3f167b"
"2"     "US"        "9a24e339723632c1f8d4ceb82b6aa098"
"3"     "US"        "021109a71c26e252f75a69905da79d27"
"4"     "US"        "b5f7718d108c9fbc3ad546832d3632d3"
"5"     "SE"        "382155ea04502c976fccbab35dcce290"
"6"     "SE"        "79c1ff6bac2c3c36495ee9c08fc8c211"
"7"     "US"        "21e2eb330732e6d74fc19e260dd5f26f"
"8"     "US"        "e6ef5608014f4e9b697a217010c801a6"
"9"     "SE"        "a53b3d20ada68715b07d09cde2d1e7ba"
"10"    "US"        "08d448b86a3b2f7d05a721ef18a8f02f"
"11"    "US"        "a9ec1a4ce8784249a4ae1c400cc75c8f"
"12"    "SE"        "cedfb21356dd656fe2fd9b2442342b10"
"13"    "US"        "26314a78584de4efcb2b3b4069ba2c43"
"14"    "US"        "b180e756567fb9896e77ee05da9d9b14"

Answer 1

利用JOIN

SELECT t1.id
  FROM table1 t1 JOIN table1 t2
    ON t2.hashKey = '08d448b86a3b2f7d05a721ef18a8f02f'
   AND t1.id < t2.id

注意：根据 MySQL 的版本，基于连接的查询有更好的机会得到适当的优化。

输出：

| 身份证 |
|----|
| 1 |
| 2 |
| 3 |
| 4 |
| 5 |
| 6 |
| 7 |
| 8 |
| 9 |

这是SQLFiddle演示

Answer 2

你可以尝试这样的事情：

select id from
 myTable where id < (
   select id 
   from myTable 
   where hashkey = '@thisHash'
   );