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  1. database - How to select unique records by SQL - Stack Overflow

    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 …

  2. Get unique values from a list in python - Stack Overflow

    Oct 15, 2012 · I want to get the unique values from the following list:

  3. How to add unique field validation in nest js with class-validator

    Mar 7, 2023 · How to do validation with database like unique filed validation in nest JS using the class validator? I created a custom validation class and tried it. But userService was undefined …

  4. df.unique () on whole DataFrame based on a column

    Apr 3, 2017 · uniqueId = df["Id"].unique() I get a list of unique IDs. How can I apply this filtering on the whole DataFrame such that it keeps the structure but that the duplicates (based on "Id") …

  5. Entity Framework Core add unique constraint code-first

    The OP is asking about whether it is possible to add an Attribute to an Entity class for a Unique Key. The short answer is that it IS possible, but not an out-of-the-box feature from the EF Core …

  6. Get all unique values in a JavaScript array (remove duplicates)

    I have an array of numbers that I need to make sure are unique. I found the code snippet below on the Internet, and it works great until the array has a zero in it. I found this other script here on

  7. Difference between primary key and unique key - Stack Overflow

    Mar 5, 2012 · Unique Key (UK): It's a column or a group of columns that can identify a uniqueness in a row. Primary Key (PK): It's also a column or group of columns that can identify a …

  8. How do I create a unique constraint that also allows nulls?

    Apr 20, 2009 · I want to have a unique constraint on a column which I am going to populate with GUIDs. However, my data contains null values for this columns. How do I create the constraint …

  9. sql - How to select only the first rows for each unique value of a ...

    In the table, one customer like John Smith can have multiple addresses. I need the SELECT query for this table to return only first row found where there are duplicates in 'CName'. For …

  10. SQL to find the number of distinct values in a column

    Apr 5, 2019 · SELECT DISTINCT my_col, count(*) OVER (PARTITION BY my_col ORDER BY my_col) AS num_rows FROM my_tbl Using this OVER based approach is of course optional. …