将具有相同ID的行合并为一行，保留所有数据 [英] combined rows with same id in to one row keeping all data

问题描述

任何人都可以帮忙吗，我有一张桌子，上面有许多植物的记录.植物可以具有多个名称，该表将其显示为不同的记录.该表称为new_plantsname

Can anyone help I have a table with a number of records for plants. A plant can have a number of names the table shows this as different records. The table is called new_plantsname

plantid name
1       tree
1       rose
2       bush
3       tree
3       bush
3       rose

这将继续进行超过3000条记录

this continues for over 3000 records

我想要的是将具有相同Plantid的记录合并在一起，并在不同的列中显示不同的名称:

what i want is it to combined records with same plantid and show the different names in different columns:

plantid name1 name2 name3 ...
1       tree  rose  NULL
2       shrub NULL  NULL
3       tree  rose  bush 

等

可以帮助我查询此操作吗?我也想将结果保存到新表中

Can one help me the query to do this. I also want to save results to a new table

预先感谢

推荐答案

这基本上是一个PIVOT(您未指定RDBMS)，我假设MySQL并不具有PIVOT函数，因此您需要使用带有CASE语句的聚合函数复制此代码.此解决方案将rownumber添加到每一行，以便您确定需要转换为列的多少name值.

This is basically a PIVOT (you did not specify RDBMS) I am assuming MySQL and it does not have a PIVOT function so you will need to replicate this using an aggregate function with a CASE statement. This solution adds a rownumber to each row so you can determine how many name values you need to transform to columns.

如果您知道要拥有多少name个值，则可以对这些值进行硬编码:

If you know how many name values you are going to have you can hard-code the values:

select plantid,
  max(case when nameRn = 'name1' then name end) Name1,
  max(case when nameRn = 'name2' then name end) Name2,
  max(case when nameRn = 'name3' then name end) Name3
from
(
  select plantid, name,
      concat('name', @num := if(@plantid = `plantid`, @num + 1, 1)) as nameRn,
      @plantid := `plantid` as dummy
  from
  (
    select plantid, name, @rn:=@rn+1 overall_row_num
    from yourtable, (SELECT @rn:=0) r
  ) x
  order by plantid, overall_row_num
) src
group by plantid;

请参见带有演示的SQL提琴

如果值的数量未知，则可以使用准备好的语句来生成该值的动态版本:

If you have an unknown number of values, then you can use a prepared statement to generate a dynamic version of this:

SET @sql = NULL;
SELECT
  GROUP_CONCAT(DISTINCT
    CONCAT(
      'max(case when nameRn = ''',
      nameRn,
      ''' then name end) AS ',
      nameRn
    )
  ) INTO @sql
FROM 
(
  select plantid, name,
      concat('name', @num := if(@plantid = `plantid`, @num + 1, 1)) as nameRn,
      @plantid := `plantid` as dummy
  from
  (
    select plantid, name, @rn:=@rn+1 overall_row_num
    from yourtable, (SELECT @rn:=0) r
  ) x
  order by plantid, overall_row_num
) src;


SET @sql = CONCAT('SELECT plantid, ', @sql, ' 
                  FROM 
                  (
                    select plantid, name,
                        concat(''name'', @num := if(@plantid = `plantid`, @num + 1, 1)) as nameRn,
                        @plantid := `plantid` as dummy
                    from
                    (
                      select plantid, name, @rn:=@rn+1 overall_row_num
                      from yourtable, (SELECT @rn:=0) r
                    ) x
                    order by plantid, overall_row_num
                  ) src
                   GROUP BY plantid');

PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

请参见带演示的SQL提琴

两者都会产生相同的结果:

Both will generate the same result:

| PLANTID | NAME1 |  NAME2 |  NAME3 |
-------------------------------------
|       1 |  tree |   rose | (null) |
|       2 |  bush | (null) | (null) |
|       3 |  tree |   bush |   rose |

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