No, they aren’t the same algorithm. For starters, the LINQ OrderBy is documented as stable (i.e. if two items have the same Name, they’ll appear in their original order). It also depends on whether you buffer the query vs iterate it several times (LINQ-to-Objects, unless you buffer the result, will re-order per foreach). For the … Read more
If you are using plain LINQ-to-objects and don’t want to take a dependency on an external library it is not hard to achieve what you want. The OrderBy() clause accepts a Func<TSource, TKey> that gets a sort key from a source element. You can define the function outside the OrderBy() clause: Func<Item, Object> orderByFunc = … Read more
According to Tom Kyte: “Unless and until you add “order by” to a query, you cannot say ANYTHING about the order of the rows returned. Well, short of ‘you cannot rely on the order of the rows being returned’.” See this question at asktom.com. As for ROWNUM, it doesn’t physically exist, so it can’t be … Read more
Default sorting is ascending, you need to add the keyword DESC to both your orders: ORDER BY article_rating DESC, article_time DESC
There is no default sort order. Even if the table has a clustered index, you are not guaranteed to get the results in that order. You must use an order by clause if you want a specific order.
Use MySQL’s FIELD() function: SELECT name, description, … FROM … WHERE id IN([ids, any order]) ORDER BY FIELD(id, [ids in order]) FIELD() will return the index of the first parameter that is equal to the first parameter (other than the first parameter itself). FIELD(‘a’, ‘a’, ‘b’, ‘c’) will return 1 FIELD(‘a’, ‘c’, ‘b’, ‘a’) will … Read more
It will order first, then get the first 20. A database will also process anything in the WHERE clause before ORDER BY.
MySQL has an undocumented syntax to sort nulls last. Place a minus sign (-) before the column name and switch the ASC to DESC: SELECT * FROM tablename WHERE visible=1 ORDER BY -position DESC, id DESC It is essentially the inverse of position DESC placing the NULL values last but otherwise the same as position … Read more
No, that behavior cannot be relied on. The order is determined by the way the query planner has decided to build up the result set. simple queries like select * from foo_table are likely to be returned in the order they are stored on disk, which may be in primary key order or the order … Read more
People use different tricks to do this. I Googled and find out some results each follow different tricks. Have a look at them: Alpha Numeric Sorting in MySQL Natural Sorting in MySQL Sorting of numeric values mixed with alphanumeric values mySQL natural sort Natural Sort in MySQL Edit: I have just added the code of … Read more