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  2. Set operations (SQL) - Wikipedia

    en.wikipedia.org/wiki/Set_operations_(SQL)

    A UNION query could combine results from both tables. Note that UNION ALL does not guarantee the order of rows. Rows from the second operand may appear before, after, or mixed with rows from the first operand. In situations where a specific order is desired, ORDER BY must be used. Note that UNION ALL may be much faster than plain UNION.

  3. Merge (SQL) - Wikipedia

    en.wikipedia.org/wiki/Merge_(SQL)

    It also supports >REPLACE INTO syntax, [6] which first attempts an insert, and if that fails, deletes the row, if exists, and then inserts the new one. There is also an IGNORE clause for the INSERT statement, [ 7 ] which tells the server to ignore "duplicate key" errors and go on (existing rows will not be inserted or updated, but all new rows ...

  4. Pivot table - Wikipedia

    en.wikipedia.org/wiki/Pivot_table

    Row labels are used to apply a filter to one or more rows that have to be shown in the pivot table. For instance, if the "Salesperson" field is dragged on this area then the other output table constructed will have values from the column "Salesperson", i.e., one will have a number of rows equal to the number of "Sales Person". There will also ...

  5. Merge sort - Wikipedia

    en.wikipedia.org/wiki/Merge_sort

    In computer science, merge sort (also commonly spelled as mergesort and as merge-sort [2]) is an efficient, general-purpose, and comparison-based sorting algorithm. Most implementations produce a stable sort , which means that the relative order of equal elements is the same in the input and output.

  6. Viewshed analysis - Wikipedia

    en.wikipedia.org/wiki/Viewshed_Analysis

    The algorithm is also based on a given set of variables. When performing a viewshed analysis, several variables can be used to limit or adjust the calculation. For example, if the analysis is to determine the location of a radio tower, the height of the tower could be added to the elevation of that location (cell value).

  7. Stack trace - Wikipedia

    en.wikipedia.org/wiki/Stack_trace

    Both C and C++ (pre-C++23) do not have native support for obtaining stack traces, but libraries such as glibc and boost provide this functionality. [6] [7] In these languages, some compiler optimizations may interfere with the call stack information that can be recovered at runtime.

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    pandas merge keep all rows visible based on one field in sql server database