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What is the quickest way in Oracle SQL to find out if one or more duplicates exist in a table?


What is the quickest way in Oracle SQL to find out if one or more duplicates exist in a table?

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What is the quickest way in Oracle SQL to find out if one or more duplicates exist in a table?
Tag : sql , By : user121501
Date : November 28 2020, 11:01 PM

will help you I'm looking to create a statement that stops and returns true the very second it finds a duplicate value on a column. I don't care what the value is and simply need to know whether a duplicate exists or not; nothing else. , You would use exists. This returns all the duplicates:
select t.*
from mytable t
where exists (select 1
              from mytable t t2
              where t2.some_id = t.some_id and t2.rowid <> t.rowid
             );
select 1 as HasDuplicate
from (select t.*
      from mytable t
      where exists (select 1
                    from mytable t t2
                    where t2.some_id = t.some_id and t2.rowid <> t.rowid
                   )
     ) t
where rownum = 1;

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Find if Duplicates Exist SML NJ


Tag : function-programming , By : Gabe
Date : March 29 2020, 07:55 AM
it fixes the issue As @Marcin said in the comment, an easy and efficient way is to use set for checking duplication. SML/NJ have many set structures available in Utility Library.
Regarding your function, you cannot compare x and myFunc xs since they may not have the same type. And empty list is a list without duplication (myFunc [] should return false).
fun duplicated [] = false
  | duplicated (x::xs) = (List.exists (fn y => x = y) xs) orelse (duplicated xs)

Oracle/SQL - Find records that or null or may not exist or are null in another table


Tag : sql , By : August
Date : March 29 2020, 07:55 AM
it helps some times What I'm trying to do is return all the records my persons table that do not exist in secondary table or that do exist, but only if one they have null values in one of two specific fields. So given the following tables , You could write:
SELECT *
  FROM persons
 WHERE person_id NOT IN
        ( SELECT p_id
            FROM secondary_table
           WHERE colA IS NOT NULL
             AND colB IS NOT NULL
        )
;

Quickest way to find the maximum value from one column with multiple duplicates in others?


Tag : r , By : user187383
Date : March 29 2020, 07:55 AM
this one helps. In reality I have a very large data frame. One column contains an ID and another contains a value associated with that ID. However, each ID occurs multiple times with differing values, and I wish to record the maximum value for each ID while discarding the rest. Here is a replicable example using the quakes dataset in R:
library(plyr)
ddply(data, "stations", function(data){data[which.max(data$mag),]})
       lat   long depth mag stations
1   -27.21 182.43    55 4.6       10
2   -27.60 182.40    61 4.6       11
3   -16.24 168.02    53 4.7       12
4   -27.38 181.70    80 4.8       13
-----
> data2 <- data[order(data$mag,decreasing=T),]
> data2[!duplicated(data2$stations),]
        lat   long depth mag stations
152  -15.56 167.62   127 6.4      122
15   -20.70 169.92   139 6.1       94
17   -13.64 165.96    50 6.0       83
870  -12.23 167.02   242 6.0      132
1000 -21.59 170.56   165 6.0      119
558  -22.91 183.95    64 5.9      118
109  -22.55 185.90    42 5.7       76
151  -23.34 184.50    56 5.7      106
176  -32.22 180.20   216 5.7       90
275  -22.13 180.38   577 5.7      104
> library(data.table)
> data <- data.table(data)
> data[,.SD[which.max(mag)],by=stations]
     stations    lat   long depth mag
  1:       41 -23.46 180.11   539 5.0
  2:       15 -13.40 166.90   228 4.8
  3:       43 -26.00 184.10    42 5.4
  4:       19 -19.70 186.20    47 4.8
  5:       11 -27.60 182.40    61 4.6
 ---                                 
 98:       77 -21.19 181.58   490 5.0
 99:      132 -12.23 167.02   242 6.0
100:      115 -17.85 181.44   589 5.6
101:      121 -20.25 184.75   107 5.6
102:      110 -19.33 186.16    44 5.4  

Find duplicates that all equal the same value in another table in oracle sql


Tag : sql , By : user116330
Date : March 29 2020, 07:55 AM
wish of those help this may be an easy query but I'm new and I can't figure it out. I have a table with orders and another table with the location those orders came from. There is a common key between them. The problem is that one order can come from more than one location and I need to find the orders that came only from one location. , this will work:
create table t11(col1 varchar(20),col2 varchar(20));
create table t22(col3 varchar(20),col4 varchar(20));

insert into t11 values('00567','128');
insert into t11 values('00689','128');
insert into t11 values('00567','291');
insert into t11 values('00689','128');
insert into t11 values('00336','321');
insert into t11 values('00336','128');
insert into t11 values('00189','499');

insert into t22 values('128','CA');
insert into t22 values('291','LA');
insert into t22 values('321','BI');
insert into t22 values('499','GA');

select col1 from(SELECT  col1 FROM t11,t22 where 
t11.col2=t22.col3 
and t11.col1 in (SELECT col1 FROM t11 group by col1 having count(col1)>1)
and t22.col4='CA') group by col1 having count(col1)>1;
00689

Quickest way to find out if record exist


Tag : sql , By : user112141
Date : March 29 2020, 07:55 AM
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