MySQL - 如何找到开头最相似的单词

Question

如何在MySQL数据库中找到与指定单词开头最相似的varchar单词？

例如:

+-------------------+
|    word_column    | 
+-------------------+
| StackOferflow     |
| StackExchange     |
| MetaStackExchange |
|       ....        |
+-------------------+

查询:调用 get_with_similar_begin('StackExch_bla_bla_bla');
输出:'StackExchange'

查询:调用 get_with_similar_begin('StackO_bla_bla_bla');
输出:'StackOferflow'

---

更新:

Select * from words where word_column like 'StackExch_bla_bla_bla' 不会给出正确的结果，因为 'StackExchange' 与此过滤器不匹配。

附加信息:我在word_column 上有BTREE-index，我想尽可能使用它

Answer 1

在 SQL Server 中，我们可以像下面的查询一样使用 CTE 来实现您想要的:

declare @search nvarchar(255) = 'StackExch_bla_bla_bla';

-- A cte that contains `StackExch_bla_bla_bla` sub-strings: {`StackExch_bla_bla_bla`, `StackExch_bla_bla_bl`, ...,  `S`}
with cte(part, lvl) as (  
    select @search, 1
    union all 
    select substring(@search, 1, len(@search) - lvl), lvl + 1
    from cte
    where lvl < len(@search)
), t as (   -- Now below cte will find match level of each word_column
    select t.word_column, min(cte.lvl) matchLvl
    from yourTable t
    left join cte
      on t.word_column like cte.part+'%'
    group by t.word_column
)
select top(1) word_column
from t
where matchLvl is not null   -- remove non-matched rows
order by matchLvl;

SQL Server Fiddle Demo

我需要更多时间在 MySQL 中找到解决方法，希望 MySQL 专家更快地回答 ;)。

我在 MySQL 中的最佳尝试是这样的:

select tt.word_column
from (
  select t.word_column, min(lvl) matchLvl
  from yourTable t
  join (
    select 'StackExch_bla_bla_bla' part, 1 lvl
    union all select 'StackExch_bla_bla_bl', 2
    union all select 'StackExch_bla_bla_b', 3
    union all select 'StackExch_bla_bla_', 4
    union all select 'StackExch_bla_bla', 5
    union all select 'StackExch_bla_bl', 6
    union all select 'StackExch_bla_b', 7
    union all select 'StackExch_bla_', 8
    union all select 'StackExch_bla', 9
    union all select 'StackExch_bl', 10
    union all select 'StackExch_b', 11
    union all select 'StackExch_', 12
    union all select 'StackExch', 13
    union all select 'StackExc', 14
    union all select 'StackEx', 15
    union all select 'StackE', 16
    union all select 'Stack', 17
    union all select 'Stac', 18
    union all select 'Sta', 19
    union all select 'St', 20
    union all select 'S', 21
  ) p on t.word_column like concat(p.part, '%')
  group by t.word_column
  ) tt
order by matchLvl
limit 1;

我认为通过创建存储过程并使用临时表将值存储在 p 子选择中，您可以实现您想要的 -HTH ;)。

MySQL Fiddle Demo