You have a couple options here: pd.infer_freq pd.tseries.frequencies.to_offset I suspect that errors down the road are caused by the missing freq. You are absolutely right. Here’s what I use often: def add_freq(idx, freq=None): “””Add a frequency attribute to idx, through inference or directly. Returns a copy. If `freq` is None, it is inferred. “”” idx … Read more
From a purely querying standpoint, it makes no difference whether your key is descending or ascending if you want to pull N most recent or N oldest records: The internal algorithms of SQL Server can navigate equally efficiently in both directions on a single-column index, regardless of the sequence in which the keys are stored. … Read more
In python, it’s called slicing. Here is an example of python’s slice notation: >>> list1 = [‘a’,’b’,’c’,’d’,’e’,’f’,’g’,’h’, ‘i’, ‘j’, ‘k’, ‘l’] >>> print list1[:5] [‘a’, ‘b’, ‘c’, ‘d’, ‘e’] >>> print list1[-7:] [‘f’, ‘g’, ‘h’, ‘i’, ‘j’, ‘k’, ‘l’] Note how you can slice either positively or negatively. When you use a negative number, it … Read more
If you’re using SQL Server 2008 (won’t work for earlier version) there is the concept of a filtered index. You can create the index on a filtered subset of the table. CREATE UNIQUE INDEX indexName ON tableName(columns) INCLUDE includeColumns WHERE columnName IS NOT NULL
The Oracle documentation has an excellent set of considerations for indexing choices: http://download.oracle.com/docs/cd/B28359_01/server.111/b28274/data_acc.htm#PFGRF004 Update for 19c: https://docs.oracle.com/en/database/oracle/oracle-database/19/tgdba/designing-and-developing-for-performance.html#GUID-99A7FD1B-CEFD-4E91-9486-2CBBFC2B7A1D Quoting: Consider indexing keys that are used frequently in WHERE clauses. Consider indexing keys that are used frequently to join tables in SQL statements. For more information on optimizing joins, see the section “Using Hash Clusters for Performance”. … Read more
Because arrays are mutable. The index of any given item can and will change if items are added to or removed from the array. You want your key to be a unique value identifying only your unique component. A primary key that you create is always better than using an index. Here is an example. … Read more
PriceList[0] is a float. PriceList[0][1] is trying to access the first element of a float. Instead, do PriceList[0] = PriceList[1] = …code omitted… = PriceList[6] = PizzaChange or PriceList[0:7] = [PizzaChange]*7
Basically an index-organized table is an index without a table. There is a table object which we can find in USER_TABLES but it is just a reference to the underlying index. The index structure matches the table’s projection. So if you have a table whose columns consist of the primary key and at most one … Read more
Just reindex df.reindex(reorderlist) Out[89]: Age G Tm Year id Player Maurice Baker 25 7 VAN 2004 5335 Adrian Caldwell 31 81 DAL 1997 6169 Ratko Varda 22 60 TOT 2001 13950 Ryan Bowen 34 52 OKC 2009 6141 Cedric Hunter 27 6 CHH 1991 2967 Update info you have multiple players with same name out … Read more
Creating 20,000 tables is a bad idea. You’ll need 40,000 tables before long, and then more. I called this syndrome Metadata Tribbles in my book SQL Antipatterns Volume 1. You see this happen every time you plan to create a “table per X” or a “column per X”. This does cause real performance problems when … Read more