CODEWITHSUNDEEP
sqlpostgresql
Stefan S.
Stefan S.

Reputation: 4103

How to Compare Multiple Columns and Rows of a Table

I have a big data table that looks something like this

ID    Marker    Value1    Value2
================================
1     A         10        11
1     B         12        13
1     C         14        15
2     A         10        11
2     B         13        12
2     C
3     A         10        11
3     C         12        13

I want to search this data by the following data, which is user input and not stored in a table:

Marker    Value1    Value2
==========================
A         10        11
B         12        13
C         14        14

The result should be something like this:

ID    Marker    Value1    Value2    Match?
==========================================
1     A         10        11        true
1     B         12        13        true
1     C         14        15        false
2     A         10        11        true
2     B         13        12        true
2     C                             false  
3     A         10        11        true
3     C         12        13        false

And ultimately this (the above table is not necessary, it should demonstrate how these values came to be):

ID    Matches    Percent
========================
1     2          66%
2     2          66%
3     1          33%

I'm searching for the most promising approach to get this to work in SQL (PostgreSQL to be exact).

My ideas:

  1. Create a temporary table, join it with the above one and group the result
  2. Use CASE WHEN or a temporary PROCEDURE to only use a single (probably bloated) query

I'm not satisified with either approach, hence the question. How can I compare two tables like these efficiently?

Upvotes: 0

Views: 74

Answers (3)

user330315
user330315

Reputation:

The user input can be supplied using a VALUES clause in a common table expression and that can then be used in a left join with the actual table. 

with user_input (marker, value1, value2) as (
  values 
    ('A', 10, 11),
    ('B', 12, 13),
    ('C', 14, 14)
)
select d.id,
       count(*) filter (where (d.marker, d.value1, d.value2) is not distinct from (u.marker, u.value1, u.value2)), 
       100 * count(*) filter (where (d.marker, d.value1, d.value2) is not distinct from (u.marker, u.value1, u.value2)) / cast(count(*) as numeric) as pct
from data d
  left join user_input u on (d.marker, d.value1, d.value2) = (u.marker, u.value1, u.value2)
group by d.id
order by d.id;

Returns: 

id | count | pct  
---+-------+------
 1 |     2 | 66.67
 2 |     2 | 66.67
 3 |     1 | 50.00

Online example: https://rextester.com/OBOOD9042

Edit

If the order of the values isn't relevant (so (12,13) is considered the same as (13,12) then the comparison gets a bit more complicated. 

with user_input (marker, value1, value2) as (
  values 
    ('A', 10, 11),
    ('B', 12, 13),
    ('C', 14, 14)
)
select d.id,
       count(*) filter (where (d.marker, least(d.value1, d.value2), greatest(d.value1, d.value2)) is not distinct from (u.marker, least(u.value1, u.value2), greatest(u.value1, u.value2)))
from data d
  left join user_input u on (d.marker, least(d.value1, d.value2), greatest(d.value1, d.value2)) = (u.marker, least(u.value1, u.value2), greatest(u.value1, u.value2))
group by d.id
order by d.id;

Upvotes: 1

Saeid Amini
Saeid Amini

Reputation: 1307

Try this:

CREATE TABLE #Temp
(
    Marker nvarchar(50),
    Value1 nvarchar(50),
    Value2 nvarchar(50)
)

INSERT INTO #Temp Values ('A', '10', '11')
INSERT INTO #Temp Values ('B', '12', '13')
INSERT INTO #Temp Values ('C', '14', '14')


SELECT m.Id, m.Marker, m.Value1, m.Value2, 
  (Select 
    CASE
        WHEN COUNT(*) = 0 THEN 'False'
        WHEN COUNT(*) <> 0 THEN 'True'
    END
    FROM #Temp t 
    WHERE t.Marker = m.Marker and t.Value1 = m.Value1 and t.Value2 = m.Value2) as Matches

FROM [Test].[dbo].[Markers] m
ORDER BY Matches DESC

Drop TABLE #Temp

enter image description here

If it's exactly what you want, I try to solve the second part of it.

Upvotes: 1

The Impaler
The Impaler

Reputation: 48865

You can use a CTE to pre-compute the matches. Then a simple aggregation will do the trick. Assuming your parameters are:

Marker    Value1    Value2
==========================
m1        x1        y1
m2        x2        y2
m3        x3        y3

You can do:

with x as (
  select
    id,
    case when 
       marker = :m1 and (value1 = :x1 and value2 = :y1 or value1 = :y1 and value2 = :x1)
    or marker = :m2 and (value1 = :x2 and value2 = :y2 or value1 = :y2 and value2 = :x2)
    or marker = :m3 and (value1 = :x3 and value2 = :y3 or value1 = :y3 and value2 = :x3)
    then 1 else 0 end as matches
  from t
)
select
  id,
  sum(matches) as matches,
  100.0 * sum(matches) / count(*) as percent
from x
group by id

Upvotes: 1

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