duplicates
How to remove duplicates based on a key in Mongodb?
This answer is obsolete : the dropDups option was removed in MongoDB 3.0, so a different approach will be required in most cases. For example, you could use aggregation as suggested on: MongoDB duplicate documents even after adding unique key. If you are certain that the source_references.key identifies duplicate records, you can ensure a unique index … Read more
Force MySQL to return duplicates from WHERE IN clause without using JOIN/UNION?
I’m not sure why you want to ban JOIN as its fairly essential to SQL. It’s like banning function calls in a functional language. A good way to solve this is to create a result set containing the ids you want to return and join with it. Here’s one way to do it: SELECT Table1.* … Read more
PHP: Check for duplicate values in a multidimensional array
This will remove duplicate items from your array using array_unique(): $new_arr = array_unique($arr, SORT_REGULAR);
How to count the consecutive duplicate values in an array?
It can be done simply manually: $arr = array(1,1,1,2,2,3,3,1,1,2,2,3); $result = array(); $prev_value = array(‘value’ => null, ‘amount’ => null); foreach ($arr as $val) { if ($prev_value[‘value’] != $val) { unset($prev_value); $prev_value = array(‘value’ => $val, ‘amount’ => 0); $result[] =& $prev_value; } $prev_value[‘amount’]++; } var_dump($result);
Removing duplicate rows (based on values from multiple columns) from SQL table
Sample SQL FIDDLE 1) Use CTE to get max ship code value record based on ARDivisionNo, CustomerNo for each Customers WITH cte AS ( SELECT*, row_number() OVER(PARTITION BY ARDivisionNo, CustomerNo ORDER BY ShipToCode desc) AS [rn] FROM t ) Select * from cte WHERE [rn] = 1 2) To Delete the record use Delete query … Read more
Remove consecutive duplicates in a NumPy array
a[np.insert(np.diff(a).astype(np.bool), 0, True)] Out[99]: array([0, 1, 3, 2, 3]) The general idea is to use diff to find the difference between two consecutive elements in the array. Then we only index those which give non-zero differences elements. But since the length of diff is shorter by 1. So before indexing, we need to insert the … Read more
How to do unique constraint works with NULL value in MySQL
No, MySQL is doing the right thing, according to the SQL-99 specification. https://mariadb.com/kb/en/sql-99/constraint_type-unique-constraint/ A UNIQUE Constraint makes it impossible to COMMIT any operation that would cause the unique key to contain any non-null duplicate values. (Multiple null values are allowed, since the null value is never equal to anything, even another null value.) If you … Read more
How to bulk insert only new rows in PostreSQL
Import data COPY everything to a temporary staging table and insert only new titles into your target table. CREATE TEMP TABLE tmp(title text); COPY tmp FROM ‘path/to/file.csv’; ANALYZE tmp; INSERT INTO tbl SELECT DISTINCT tmp.title FROM tmp LEFT JOIN tbl USING (title) WHERE tbl.title IS NULL; IDs should be generated automatically with a serial column … Read more