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Dynamic column in SELECT statement postgres


By : Mason Dickerson
Date : October 17 2020, 11:12 AM
With these it helps In order to write a dynamic query you would have to do something like:
code :


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Oracle - dynamic column name in select statement


By : user1015328
Date : March 29 2020, 07:55 AM
To fix the issue you can do You can't vary a column name per row of a result set. This is basic to relational databases. The names of columns are part of the table "header" and a name applies to the column under it for all rows.

Mybatis dynamic column in select statement


By : Rydawg
Date : March 29 2020, 07:55 AM
fixed the issue. Will look into that further its cannot becauase your parameter is map so you can change like this and try that
code :
//call the dao method
String columns = "first_name";
HashMap map = new HashMap();
map.put("userId",userId);
map.put("columns",columns);
userDao.sample(map);

//call mapper
List<User> sample(HashMap map);

//mapper
<select id="sample" resultMap="user" parameterType="map">
    SELECT
        #{columns}
    FROM
        user
    WHERE
        userId = #{userId}
</select>

SQL SELECT statement with dynamic column names


By : bhussain
Date : March 29 2020, 07:55 AM
it helps some times I try to select columns which names are the content of other columns. I'm using MySQL 5.6. , You need some sort of case expression:
code :
select t1.id,
       (case when t2.type = 'i1' then cast(val_int_1 as varchar(255))
             when t2.type = 'i2' then cast(val_int_2 as varchar(255))
             when t2.type = 's1' then val_string_1
             when t2.type = 's2' then val_string_2
        end) as val
from table1 t1 cross join
     table2 t2;

dynamic join based on select column content (postgres)


By : user3328213
Date : March 29 2020, 07:55 AM
wish help you to fix your issue Any single query cannot return a varying number of columns. You can however include all possible values or return the results as JSON. On the bright side, you have a limited number of different OSes, so this is doable.
code :
SELECT
  profile.name, profile.ver,
  oslist.name AS os,
  android.release AS android_release, android.image, android.root,
  linux.distro, linux.env,
  windows.release AS windows_release, windows.sp
FROM profile
  LEFT JOIN oslist ON (oslist.id = profile.os)
  LEFT JOIN android ON (profile.os = 1 AND android.id = profile.os_id)
  LEFT JOIN linux ON (profile.os = 2 AND linux.id = profile.os_id)
  LEFT JOIN windows ON (profile.os = 3 AND windows.id = profile.os_id)
WHERE profile.id = 223
SELECT
  jsonb_strip_nulls(
    jsonb_build_object(
      'name', profile.name,
      'version', profile.ver,
      'os', oslist.name,
      'release', coalesce(android.release, windows.release),
      'image', android.image,
      'root', android.root,
      'distro', linux.distro,
      'env', linux.env,
      'sp', windows.sp
    )
  ) AS result
FROM profile
  LEFT JOIN oslist ON (oslist.id = profile.os)
  LEFT JOIN android ON (profile.os = 1 AND android.id = profile.os_id)
  LEFT JOIN linux ON (profile.os = 2 AND linux.id = profile.os_id)
  LEFT JOIN windows ON (profile.os = 3 AND windows.id = profile.os_id)
WHERE profile.id=223
+----------------------------------------------------------------------------------+
| result                                                                           |
+----------------------------------------------------------------------------------+
| { "name": "helloworld", "version": "1.0.0", "distro": "arch", "env": "openbox" } |
+----------------------------------------------------------------------------------+

Postgres Select Statement, column Does Not Exist


By : were
Date : March 29 2020, 07:55 AM
I hope this helps you . The problem is illustrated in the following blog post:
https://www.postgresql.org/message-id/18195.1038530280@sss.pgh.pa.us
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