How to select unique records by SQL

Question

When I perform  SELECT   FROM table  I got results like below   1 item1 data1 2 item1 data2 3 item2 data3 4 item3 data4   As you can see  there are dup records from column2  item1 are dupped   So how could I just get result like this   1 item1 data1 2 item2 data3 3 item3 data4   Only one record are returned from the duplicate  along with the rest of the unique records

User · Answer

If you only need to remove duplicates then use DISTINCT  GROUP BY should be used to apply aggregate operators to each group  GROUP BY v DISTINCT

User · Answer

just use inner join because group by won t work with multiple columns saying not contained in either an aggregate function   SELECT a   FROM yourtable a INNER JOIN     SELECT yourcolumn      MIN id  as id   FROM yourtable    GROUP BY yourcolumn   AS b   ON a yourcolumn  b yourcolumn   AND a id   b id

User · Answer

With the distinct keyword with single and multiple column names  you get distinct records   SELECT DISTINCT column 1  column 2      FROM table name

User · Answer

Select Eff st  from   select EFF ST ROW NUMBER   over PARTITION BY eff st  XYZ                          - from ABC CODE DIM    where XYZ  1 order by EFF ST fetch first 5 row only

User · Answer

I find that if I can t use DISTINCT for any reason  then GROUP BY will work

User · Answer

To get all the columns in your result you need to place something as   SELECT distinct a  Table   FROM Table   it will place a as the first column and the rest will be ALL of the columns in the same order as your definition  This is  column a will be repeated

User · Answer

It depends on which rown you want to return for each unique item   Your data seems to indicate the minimum data value so in this instance for SQL Server   SELECT item  min data  FROM  table GROUP BY item

User · Answer

There are 4 methods you can use    DISTINCT GROUP BY Subquery Common Table Expression  CTE  with ROW NUMBER     Consider the following sample TABLE with test data       Create test table    CREATE TEMPORARY TABLE dupes word text  num int  id int        Add test data with duplicates    INSERT INTO dupes word  num  id  VALUES   aaa   100  1           bbb   200  2           ccc   300  3           bbb   400  4           bbb   200  5      -- duplicate          ccc   300  6      -- duplicate          ddd   400  7           bbb   400  8      -- duplicate          aaa   100  9      -- duplicate          ccc   300  10     -- duplicate   Option 1  SELECT DISTINCT  This is the most simple and straight forward  but also the most limited way   SELECT DISTINCT word  num  FROM    dupes ORDER BY word  num      word num  ---- ---  aaa  100  bbb  200  bbb  400  ccc  300  ddd  400       Option 2  GROUP BY  Grouping allows you to add aggregated data  like the min id   max id   count     etc   SELECT  word  num  min id   max id   count    FROM    dupes GROUP BY word  num ORDER BY word  num      word num min max count  ---- --- --- --- -----  aaa  100   1   9     2  bbb  200   2   5     2  bbb  400   4   8     2  ccc  300   3  10     3  ddd  400   7   7     1       Option 3  Subquery  Using a subquery  you can first identify the duplicate rows to ignore  and then filter them out in the outer query with the WHERE NOT IN  subquery  construct       Find the higher id values of duplicates  distinct only added for clarity        SELECT  distinct d2 id     FROM    dupes d1         INNER JOIN dupes d2 ON d2 word d1 word AND d2 num d1 num     WHERE d2 id  gt  d1 id     id  --   5   6   8   9  10          Use the previous query in a subquery to exclude the dupliates with higher id values    SELECT    FROM    dupes WHERE   id NOT IN       SELECT  d2 id     FROM    dupes d1         INNER JOIN dupes d2 ON d2 word d1 word AND d2 num d1 num     WHERE d2 id  gt  d1 id   ORDER BY word  num      word num id  ---- --- --  aaa  100  1  bbb  200  2  bbb  400  4  ccc  300  3  ddd  400  7       Option 4  Common Table Expression with ROW NUMBER    In the Common Table Expression  CTE   select the ROW NUMBER    partitioned by the group column and ordered in the desired order   Then SELECT only the records that have ROW NUMBER     1   WITH CTE AS       SELECT                row number   OVER PARTITION BY word  num ORDER BY id  AS row num     FROM    dupes   SELECT  word  num  id  FROM    cte WHERE   row num   1 ORDER BY word  num      word num id  ---- --- --  aaa  100  1  bbb  200  2  bbb  400  4  ccc  300  3  ddd  400  7

[sql] How to select unique records by SQL

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